Requiem's 1-13 Alliance Grinding Guide
UPDATE:I'm turning this guide into a sort of prequel to FinaL.FreeDoM's grinding guide, as there is no need for a 1-30 I will make a it a 1-13 (and FinaL.FreeDoM's guide picks up from there).
This guide helps grind to level 13 the quickest way possible. I suggest doing Jame's leveling guide afterwards, which makes questing faster than grinding and you get to do a lot of the more fun things that you can't do whilst grinding.
Tips:
Get one gathering profession, and get skinning.
Get First Aid, IT WILL HELP. The four exceptions to this are, of course, the four classes that can heal, Priest, Paladin, Druid, or Shaman.
Buy armour off merchants and/or auction house. People say not too, they say it wastes money, but especially armour reliant classes like Warriors and Rogues need new armour almost every five levels, buy the cheapest armour that will still be useful to you.
Specc your talents in the tree that will do the most damage.
-Druids: Feral
-Hunters: Beast Mastery or MarksMan
-Mage: Fire
-Paladin: Retribution (this talent tree is best for leveling, and arguably nothing else)
-Priest: Shadow
-Rogue: Combat or Assassination
-Shaman: Elemental AND Enhancement
-Warlock: Affliction (A lot of people say Demonology is better, I personally love Affliction much more but if you feel the need to try them both go ahead)
-Warrior: Arms or Fury
Always get quests related to what you are grinding (i.e., kill X amount of Y, or gather X off of Y), hey, you're grinding them anyway, why not get an extra EXP boost?
Listen to music. Grinding may be quick in most aspects, but it's BORING. Have something to keep your mind off of it. Listening to comedians are good too.
If you have the time, run and instance! Go into LFG when you begin grinding, when your group is full stop grinding and run the instance, go back to grinding afterwards. I would not, however, suggest running nothing but instances, limit yourself to one or two times a day.
Don't turn in quests the second you finish them, wait 'til you're done grinding in that area to turn it in.
ALWAYS ALWAYS Log out at an inn, the rested exp adds up.
Don't change your Hearthstone location unless I ask you too.
If you are not a caster, buy throwing knives or a gun/crossbow/bow. If you are a paladin use judgement spells if I tell you to pull with ranged.
The Guide:
If you are Draenei/Night Elf/Dwarve/Gnome you have two choices:
Run from your starting area to Northshire Abbey or stay at your starting area until around level 12-13. Gnomes and Dwarves I suggest you run to Northshire Abbey, but Night Elfs and Draeneis it's not really worth it for you. I will add grinding guides to these areas, but if you have one and.or have an idea of how to grind please PM me about it, all credit will go to you. 
If you are Human you're sitting pretty, follow the guide as is:
ELWYNN FOREST
LEVEL 1-4
1: Take the Quest 'A Threat Within' from the first NPC you meet named Deputy Willem.
2: Turn it in to Marshal McBride inside the churchlike building. Get the follow-up 'Kobold Camp Cleanup'
3: Go back outside and kill wolves until you hit level 3 sell and repair and get the quest 'Eagan Peltskinner' from Deputy Willem.
4: Go around the outside of the church and turn in 'Eagan Peltskinner' to the NPC of the same name. Get the follow-up 'Wolves Across the Border.'
5: Kill Wolves until you are level 4 and have completed 'Wolves Across the Border.' Turn it in. Sell and repair.
LEVEL 4-8
1: Go kill Kobolds until you ding level 6 and you have completed 'Kobold Camp Cleanup.' Sell and repair. Turn it in to Marshal McBride, don't get the follow-up but do get your class quest, it will be called 'Something Letter' (the something will vary based on what class you are. If Marshal McBride doesn't have a quest called 'Something Letter' for you, it means your class quest is not available with him, this will only happen if you are not a class humans can play).
2: Inside the church find your class trainer (represented by the little question mark on the mini-map) and turn in 'Something Letter,' if you are a warlock or priest another class quest will be waiting for you. Get that class quest, warlocks go do it because it is important and in the immediate area, if you are a priest hold on to it we will give you a chance to do it later. Buy class skills.
3: Now go to the Kobold camp where you grinded to six, and go north until you reach a cave with Kobolds. Grind here until level 8.
LEVEL 8-11
1: Outside the church follow the road south, get 'Rest and Relaxation' from Falkhaan Isenstrider. Continue south until you hit Goldshire. Go to the inn and turn in 'Rest and Relaxation' to Innkeeper Farley, also bind there (by bind I mean "make this inn your home," it makes you able to to warp from wherever in the world you are to your home-inn with your hearthstone). If you are a priest you should see another blip on your minimap, go upstairs and turn in your class quest, get the follow-ups and do them, when you have reached the end (which results in you getting a robe) continue from here. If you aren't a priest continue on with this guide.
2: Go outside the inn and get the quest 'A Fishy Peril' from Remy "Two Times" and turn it in to Marshal Dughan. Ge the follow-up 'Further Concerns.'
3: Look around at the vendors in Goldshire until you find someone with a skinning knife and buy one.
4: From Goldshire head on the North east and you will come to a lake called Crystal Lake. This lake has surplus murlocs. Circle around the lake killing every murloc you see until level 10.
(NOTE: The skinner trainer lives in the house that's right next to Crystal Lake, drop in and train up)
5: Go back to Goldshire and learn your class skills. Start heading east and go to the Eastvale Logging Camp at around (81,65). On route there you should meet Guard Thomas, who's standing near a bridge. Turn in 'Further Concern' and don't get any follow-ups. Get 'Fine Linen Goods' from Sara Timberlain, she's around (79,68). Go west from Sara until you come to a stream, from there head north and you will come to a lake with a big Island in the middle (the lake is called "Stone Cairn Lake"). Go to the big island and grind Defias until level 11 (if you run out of Defias, there are murlocs on the east cost) and you have completed 'Fine Linen Goods,' go and turn it in.
6: Now that you are level 11 and have turned in 'Fine Linen Goods' to Sara Timberlain Hearthstone to Goldshire, make your way on the road heading North west to Stormwind. Get the flightpath there and visit your trainer. Ask the guard if you don't know where s/he is. You will also have talent points now. Select wisely which talents you want to use for they are expensive to undo. If you are any class Besides Paladin, Rogue, or Priest your class trainers should have another quest for you. Complete the quests and continue on with the guide.
LEVEL 11-13
1: Walk back to Goldshire (if your heartstone cooldown is done, hearthstone). Get the quest 'Westbrook Garrison Needs Help!' Then take the road west to (24,77) (or thereabouts) Get 'Wanted: "Hogger" ' from the poster, go into the tower ahead and turn in 'Westbrook Garrison Need Help!' and then go south until you run into Gnolls called Riverpaws. Kill gnolls until level 12, avoiding Hogger (who is an elite gnoll) if you can.
2: At level 12 you should be able to solo him. Go to (25, 92) and kill him, loot his claw for the quest. If you try and try but can't kill him just abandon the quest, it's not worth to much effort. Grind again afterwards until level 13. If, whilst you are grinding, a scroll called "The Collectors Schedule" drops off one of the gnolls right-click it and start the quest, if it doesn't don't fret it's optional. Your Hearthstone's cooldown should be over so hearth back to Goldshire and turn in 'Wanted: "Hogger" ' and 'The Collector' to Marshal Dughan. Don't get any follow-ups from Marshal Dughan. You are now done with Elwynn and should be level 13. Visit your class trainer and then go on to FinaL.FreeDoM's guide.
Requiem's 30-50 Alliance Grinding Guide
I suggested doing Jame's levelling guide after my 1-30 guide. But wait... you want to continue grinding? No problem. Follow on here from where my other guide left off.
If you are just picking up from here, that's fine too. Just go to the section where it tells your level where to grind and jump right in! But first, I suggest going to my other guide and reading my TIPS sections.
THE GUIDE
Thousand Needles
Getting to Thousand Needles: If you followed my first guide you will be in Stormwind. If not, either fly to Stormwind, or Iron Forge (if you have the Flightpath), or Menethil Harbour (again, if you have the flightpath there).
If you don't have the fp to Iron Forge: Go to the Dwarven District in Stormwind, in the back there will be a portal, enter it and take the tram to Iron Forge.
In Iron Forge: Grab the Flightpath near the Great Forge and then exit Iron Forge through the gates, take the mountain path to the bottom and then follow the road south until you come to a fork in the road, go left and follow the road until you reach another fork (if you come to Kharanos you went the wrong way). Go right at the fork and you will reach Southern Gate Outpost after some distance. Go through there and you will reach Loch Modan. Follow the road north and you will come to Thelsamar off to the side, grab the flightpath there go back to the road and follow north until Algaz Pass. Through there go into the Wetlands. Follow the road, going left at each fork. This is a very long walk, but you will eventually reach an island called Menethil Harbour. If you reach Dun Modr, turn around and go the other way on the road.
At Menethil Harbour: Make the inn here your home location (if you don't know where it is look for him with Blizzards handy new Tracking Feature!) and grab the flightpath. Go around the fortress and you will be able to see the sea, and two docks. Go on the left one and wait for the boat. Take the boat to Theramore Island.
At Theramore: Grab the flightpath and leave Theramore on the road heading to Dustwallow Marsh, follow the road (its a long walk) until you reach your first fork, then go right and you will zone into the barrens. From the barrens go south toward Razorfen Downs and Razorfen Kraul until you reach the Great Lift. Go down the great lift (if you get harassed by the tauren guards there, just jump off. You will die, but the graveyard is so close by it doesn't really matter). Follow the road west until you reach the Feralas/Thousand Needles border, there will be an Alliance outpost there. Grab the flightpath there and then go east until you reach The Screeching Canyon.
Levels 30-31
1: Grind on harpies here until level 31. If you are lucky, you will also have collected 25 Vibrant Plumes. They are rare at about a 5% drop rate so don't hang around after level 31 if you don't have 25. If you don't have 25 sell at the auction house next time you go there. They sell well. If you did get 25, save them. And next time the Darkmoone fair is in town, turn them in for a 14 slot bag.
This was one of my least favourite grinding spots in the game (fun wise, I mean. EXP wise its good). But A) it's only for one level 
and B) it's good EXP.
Levels 31-33:
1: Go north until you reach a road. Follow that road south, watching out for the horde guards by Freewind Post, until you enter the Shimmering Flats. Follow the path through Shimmering Flats until you reach Mirage Raceway, get the quest "Rocket Car Parts" from Kravel Koalbeard and "Load Lightening" from Pozzik. Make wide circuits around the the race track, killing everything you see until you have reached level 33 and have finished the two quests: "Rocket Car Parts" and "Load Lightening."
NOTE: 30 car parts may seem like a lot, but they are littered everywhere, and now that patch 2.3.0 is enabled they will sparkle. You should have it done before you reach level 32.
2: When you have finished both quests and are level 33 run back to the mirage raceway and turn the quests in. Hearthstone back to Menethil Harbour and fly to Iron Forge, learn your class skills visit the auction house etc. then fly back to Menethil.
You are now done with Thousand Needles.
Hillsbrad Foothills
Getting to Hillsbrad: From Menethil follow the road out and keep following it until you came to the fork that, had you gone the wrong way, would have taken you to Dun Modr, follow the road up to Dun Modr and into the Arathi Highlands. Follow the path north from Dun Modr and you will reach the main road, follow the main road west (stopping briefly at Refuge Pointe to get its flightpath) until you zone into Hillsbrad, then continue west until a road splits off, follow that road to Southshore. Grab the flightpath there.
Levels 33-35:
1: Go back to the main road, from there go north west (you will leave the main road) and you will come to a Yeti cave. There are level 30-32 Yetis here. Grind here until level 35.
Levels 35-38:
1: When you are at level 35 run back to the main road, follow it east until another road branches off of it. Go north until you zone into Alterac. Grind on the Crushridge ogres here until level 38. When you are at level 38 hearth back to Menethil.
You are done with the Hillsbrad Foothills.
Badlands
Getting to the Badlands: Fly to Thelsamar from Menethil Harbour. From there go east until you hit the Loch (the giant lake in Loch Modan). Follow the shore of the Loch south until Grizzlepaw Ridge, from there the shore starts curving southeast, so leave the shore and go completely south, you should notice a path follow it into the Badlands.
Levels 38-40:
1:Hug the western mountain ridge, and follow it. After a lengthy walk you should reach a small goblin camp. Get "Study of the Elements: Rock" from Lotwil Veriatus. To the left of the camp there are Lesser Rock Elementals, grind here until level 40 and until you have completed "Study of the Elements: Rock."
Now you have two options: Have enough money for your mount? Good, hearthstone to Menethil and fly to whichever city sells the mount you can buy. Fly back to Thelsamar (make it your Home location, now), and zone back into Badlands and continue on with the guide.
If you don't: Continue on with the guide. I suggest you start selling more stuff on the auction house, or ask your guild (if you have one)for a lone. The sooner you get your mount, the better.
Levels 40-43:
1: Hug the mountains again and follow them north until you come to Angor Fortress, grind the Dwarves here until level 43.
2: Hearthstone back to Thelsanar (or Menethil, based on whether you had enough mount money) fly to Thelsanar if it isn't your home location and make it your home location. Repair here and go back to the Badlands.
Levels 43-45:
1: If you didn't have mount money before, it's your lucky day. In the southwestern corner of the Badlands there's a surplus of Greater Elementals. Grind on them until level 45. The Vendor loot alone should give you enough for your mount . Hearth stone to Thelsanar, and fly to Iron Forge. Sell, repair, visit the auction house. And get Prepared for a very long grind.
You are now done with Badlands.
Feralas
Ok. You should know how to get to Feralas. If you forget, just take the boat to Theramore, and then take the fp in Theramore to the Alliance base on the border of Feralas and Thousand Needles.
Levels 45-50:
1: I am going to steal an idea from FinaL.FreeDoM here and suggest you grind on the nagas in the cave on the island south of Feathermoon Stronghold. Good drops. GREAT EXP. Grind here until level 50
2: When you are done hearth to Thelsanar and fly to Iron Forge. Repair, sell, visit the auction house.
You are now done with Feralas.
End of Guide.
Grats on 50