Professions
There are two different approaches to the professional trade skills. You can choose two that will benefit your character by creating items you will be using for less money or quicker availability or you can choose strictly for profit.
I have tried both methods during the close Beta test and I found making equipment or potions for myself was better than gathering or crafting for profit and then buying any needed items off the auction house or other players. The only other difference would be if you belong to a good guild where higher-level players create items for you for little to nothing in cost.
I played warrior, shaman, mage, rouge, hunter, warlock, & paladin. I would choose the following trade skills for these classes.
Warrior & Paladin ? Herbalism & alchemy for making your own potions or Mining & Blacksmithing for making your own weapons and armor plus weapon buff stones.
Shaman & Rouge - Leathercrafting & Skinning for creating your own armor and armor patches. You can also selling your green & higher-level armor at the auction house.
Mage & Warlock ? Tailoring & enchanting for creating your own armor, bags, and enchanting items. High level enchanting and bags can be quite profitable.