I decided to write a few "tips" to cover Cataclysm Launch Day stuff for people. The Guide is aimed at Alliance, though most of it is relevant to Horde as well. If you were in Beta or have been reading a lot of the preview info, little of this is new.

Initial Preparation:
-This is probably a good time to use up old stock piles of Food and Pots, so get them ready for leveling as they wont be useful after a level or two.
-Grab your bandages if you need them, but they become useless after a level.
-Clean out your bank.
-etc, etc, (use common sense).

Hearth Stone:
-The best spot to be hearthed is in Storm Wind, this is due to the portals that open up in the NE section of the Stormwind Map to all 5 of the new Zones plus Tol Barad.
-Which Inn you Hearthstone at in Stormwind is up to you, I prefer the South myself but many will like the North as the portals are next to it and it is usually less congested.

Initial Log In Placement:
-Log your character out directly in front of "Bralla Cloudwing" (Flying Trainer-next to the Gryphon Master) in Stormwind. This is done so that immediately upon logging into the game on December 7, you can purchase the Flight Master's License (250 gold) and start flying everywhere.

Trade Skills:
The next thing you should do is grab your Trade Skill Upgrades from the Profession Trainers in Storm Wind. If your memory is rusty, go visit all your Trainers before Dec 7, so you can find them again, thus saving you time and you wont be one of the idiots in chat asking where XYZ Trainer is.

Archeology:
If your main focus is to level your character first, then I suggest to just skip Archeology until level 85. This is not a Profession that you "do while leveling", Archeology is a focused event and because of this, you can skip it until you get to level 85 and decide that you now want to do "Archeology".

However, most people will just want to go pick it up anyways, and the location is the library in the Castle in Stormwind. Speak to Harrison Jones at 85,25. FLY here, don't ride. Remember, you have flying now!

Check the Bank Auction House:
Provided it isn't midnight and you are not geared up in ICC Raid loot, it can be worth taking a few minutes to go hit up the Auction House and see if there are any level 80 "green" equipment upgrades for your character that you can buy. Don't pay inflated prices though, you will upgrade everything else eventually anyways.

A Note On Mob Difficulty:
If you are reading this, then you have probably heard by now that Mob's are harder and have more health in Cataclysm. Initially, this isn't a big issue but by level 83 or so, you will notice that Mobs hit a lot harder than their level 80-82 Cataclysm counter parts and have a LOT more health than what you find in Vashj'ir and Hyjal. Actually, the base 80 mobs in those two zones are about triple the health of level 80 zones in Northrend.

What this means is that most non-self healing type classes/specs will find that they have to stop and heal after a couple mobs and then go at it again. To me, this sucks.

Personally, my advice is to use a spec that gives up some DPS power in favor of healing yourself as you level up. (ie- Frost or Blood Death Knight vs Unholy). Myself, I prefer to kill a little slower but never stop, than kill faster but have to stop.

Where To Level First?
You have the choice of leveling in Vashj'ir or Hyjal as both are level 80 to 82 zones. To get these zones going, you need to do the starter quests that you will find appearing in Stormwind on Dec 7. Do those and they will lead you to the respective zones you want to start leveling in.

Is there any real advantage to what zone you start in?
The only real difference is that Vashj'ir is obviously a very unique zone as it takes place totally under water and it will certainly give you more of a "this is a new expansion" feel than Hyjal will. Hyjal is still awesome but it isn't unique.

For those that hate under water zones, don't worry about it. 3 or 4 quests into it, you get a permanent breathing buff and a movement speed buff and then about 15 quests in, you get a fast under water mount. You can basically think of being under water as "flying" once this happens.