Well, I was bored so I decided to make a guide(my first), most of it is common sense, but it might help a few people get exalted a lot quicker.
First off, you will need to choose which Rep to side with, the rewards can be found here:
Comparison of Aldor and Scryer rewards - WoWWiki, the Warcraft wiki
This is the general idea of how you will get to exalted.
Aldor
Friendly > Honored
Do this quest by turning in Marks of Kil'jaeden in (1 or 10 at a time)
+250 Rep per 10
-Can't turn in past Friendly
Allakhazam.com: World of Warcraft: Quest: Marks of Kil'jaeden
Honored > Exalted
Once you hit honored you can turn in Marks of Sargeras (1 or 10 at a time)
+250 Rep per 10
Allakhazam.com: World of Warcraft: Quest: Marks of Sargeras
You can also turn in Fel Armaments
+350 Rep each, and 1 Holy Dust (Used for the shoulder enchantments)
Allakhazam.com: World of Warcraft: Quest: A Cleansing Light
Quests in SMV and Netherstorm
Scryer
Friendly > Honored
Do this quest by turning in Firewing Signets in (1 or 10 at a time)
+250 Rep per 10
-Can't turn in past Friendly
http://wow.allakhazam.com/db/quest.html?wquest=10325
Honored > Exalted
Once you hit honored you can turn in Sunfury Signets (1 or 10 at a time)
+250 Rep per 10
http://wow.allakhazam.com/db/quest.html?wquest=10653
You can also turn in Arcane Tomes
+350 Rep each, and 1 Arcane Rune (Used for the shoulder enchantments)
Allakhazam.com: World of Warcraft: Quest: Synthesis of Power
Quests in SMV and Netherstorm
As opposed to grinding marks/signets and armaments/tomes from mobs like most guides tell you to, you can get rep much easier by buying them from the AH. Many people think you should farm the mobs with the best drop rates for marks/signets to get them, but instead of farming 50-60 marks/signets and a few armaments/tomes in an hour, you could grind about 150 gold and buy around 250 of the high ranking marks/signets (depending on server prices and availability) Thats almost 5 times the rep in the same amount of time.
There are tons of gold making guides on this site if you do not know how to make gold. Some of the more popular ways are:
Questing at 70(fastest if you still have a lot left)
Farming motes
Dailies
Gathering Professions
Also remember to do all of the quests for your side once AFTER you hit honored.
Aldor
http://www.giddygamer.com/wow/conten...rep_quests.pdf
Scryer
http://www.giddygamer.com/wow/conten...rep_quests.pdf
Rep while leveling: (Thanks to holmedog for the suggestion)
You can get an early start at your reputation and help save quests for 70, by grinding out marks from 65 to 70.
Locations:
Marks of Kil'jaeden - Friendly > Honored ~240 marks (about 220 for Humans)
The Bone Wastes - Terokkar (32,53)
The "Cabal" mobs are around level 63 and have ~ 30% drop rate
Marks of Sargeras
Legion Hold - SMV around (24,37)
66-68 mobs ~25-30% drop rate
Ruins East of Area 52 - Netherstorm
Artifact Seekers, they are level 66-68, good for melee classes. ~31% drop rate
Firewing Signets - Friendly > Honored ~ 240 signets
NE of Bonechewer Ruins - Terokkar
From "Firewing" mobs that are lvl 63-65, ~30% drop rate
Sunfury Signets
The Manaforges in Netherstorm
Blood Elves between levels 66-70, ~25% drop rate
TIPS:
Do not turn in any of your high ranking marks, or any of tomes/armaments until you are at least honored.
Do not do the quests until you are at least honored.
Check the AH often so you can see the average prices on your server(Scryer items are usually very cheap because they are found all over netherstorm)
If you get rep items from the other rep, you can usually trade them for your sides equivalent
It is usually cheaper to buy in bulk, and to buy high ranking marks/signets as opposed to the tomes and armaments
Sorry if you knew all of that already, i was trying to help those who didn't so please don't flame.