Wolfram01 said:
Um well starting the game out now you will find it pretty deserted as you grind and grind away, because everyone already has top level characters. Grouping for the lowbie dungeons and such will be nigh impossible.
It actually hasn't been that hard lately, which has been a huge surprise for me. Even DPS it usually only took 3-4 minutes to get a group at low levels.
That said, this is an excellent time to start. There's going to be a flood of new characters starting today as there are some huge changes happening. As people have said, there are sales on: Original and Burning Crusade expansion are 4 Pounds each, Wrath of the Lich King expansion is 8. Getting the original and Burning Crusade at least is very much recommended, though I am a sucker for Blood Elf paladins.
In-game stuff:
Consider your general playing preferences. Do you like playing a glass cannon? A tank? Either way, I'd suggest going DPS (maximizing damage) for your first character: It's a bit harder to get groups for dungeons through the built-in system, but they are easier to play and people won't blame you if things go wrong.
At level 10 you get to choose a specialization (these can be reset later for a small but increasing fee), which really define what your character does. As I said, I suggest DPS for your first character (they have a small sword to the right of their title), but other than that just pick what seems fun. At level 15 you get access to the Dungeon Finder - use it. Dungeons are great for getting better stuff and are what end-game is all about. They're also an excellent way to level as you gain xp much faster, though they can get pretty repetitive.
I wholeheartedly recommend a Paladin or a Mage. Mages are glass cannons and damage specialists, and if you go Arcane they are also quite simple to play.
My favourite profession combination is Skinning and Mining. You earn plenty of money fast with hardly any effort, though they are admittedly not all that exciting.
Edit: If you're willing to play on Stormscale, I'll be rolling a new (Horde) character today if you've got any questions while you play.