Achievements Guide:

How to use this guide: It's big and it's not in alphabetical order (the order is the one I see on my achievements screen if you're curious). This would take me a long time to rectify so I won't do it yet, but until then you can use your browser's search tool in order to find the one you need. If there's a mistake in an achievement name please let me know.


General:

Tastes Like Chicken / It's Happy Hour Somewhere:
You can most if not all of this in Shattrath and capital cities by going to different vendors (example: Meat / Fish / Mushrooms, etc...) If that's not enough hit the AH and buy some food there or cook your own. Don't worry if you already completed some of this and can't remember what you ate and drank, there's more than enough out there for you to complete this easily. Mage food also counts towards those.

25 Tabards:
Here's a list of the tabards that work for this: http://www.wowhead.com/?achievement=621
In WotLK an NPC will also allow you to buy back all the tabards you got from Reputations and will restore any quest ones you might have deleted. Others like the Horde ones are not restored since you can get them again if you destroy them.

Leading The Cavalry:
The easiest and cheapest way to do this is to get exalted with the five horde races as well as with netherwing or skyguards. Together, these 7 reputations will sell over 25 mounts and you can also buy Horde flying mounts (not a reputation). Get those that work best for you! And no, AQ mounts don't count unless you have the quest line one.

Taurens are handicaped for this achievement. Here is the list of mounts they can learn:
5 Kodos (TB)
6 Wolves (Org)
3 PvP Mounts
8 Talbuk (Mag'har)
2 Talbuk (Halla)
1 Wolf (Alterac Valley)
6 Netherwing Drakes (Netherwing)
5 Netherrays (Skyguard)
7 Wind Riders (Shadowmoon)
4 Ahn'Qiraj bugmounts
Cenarion Expedition Mount

As you can see that is only 48 mounts, taurens have to wait until WotLK or have to get rare mounts in order to complete this achievement pre-TBC (midnight, deathcharger, anzu, ZG mounts). Unless they're an engineer.

Well Read:
I recommend using Venator's Guide on Wowhead at: http://www.wowhead.com/?achievement=1244
Venartor's guide is the 9th comment on the page. Due to lack of space and the time the author took to making his guide I would rather link it than repost it, a lot of work was obviously involved.

Shop Smart, Shop Pet... Smart
The first thing you have to do is visit your faction's pet vendors.

Both Factions:
-Magus Tirth (One Thousand Needles)
-Narkk (Booty Bay)
-Dealer Rashaad (Stormspire)
-Flik (Darkmoon Faire)

Horde:
-Xan'tish (Orgrimmar)
-Jilane (Eversong Woods)
-Halpa (Thunder Bluff)

Alliance:
-Sixx (Exodar)
-Donni Anthania (Elwynn Forest)
-Lil Timmy (Stormwind, Rare)
-Shylenai (Darnassus)
-Yarlyn Amberstill (Dun Morogh)
Another piece of advice is to regularly check both the Horde and the Neutral AH, go in the Pets tab and enable "Usable Items only"
You should still be short with all these but not by much. Go on Wowhead and look at the pets list and check which ones you don't have and go for the easiest ones at this point.