What professions should I take as X class?

That question is always debatable. Multiple professions appeal to multiple classes. But I will list the ones that I know benefit each class best.

* Alchemy: All classes
* Blacksmithing: Warriors, Paladins, Rogues, Hunters, Enhancement Shaman (Maces, Axes and Mail)
* Enchanting: All classes
* Engineering: All classes
* Jewelcrafting: All classes
* Leatherworking: Rogues, Druids, Hunters, Shaman, Any class (for drums)
* Tailoring: Mage, Priest, Warlock, Elemental Shaman, Balance Druid

What are the best professions to make money?

The quickest answer to that is to take 2 gathering professions, and sell everything on the Auction House. Just in case, I will list them here.

* Herbalism
* Mining
* Skinning

It is not reccommended that you take both Herbalism and Mining at the same time as you cannot track both items at the same time.

What crafting profession makes the most money?

Ahh, here's where it gets tricky.

* Alchemy: Cheap to level (when paired with herbalism), makes money at all levels.
* Blacksmithing: Cheap to level (when paired with mining), rarely makes money, high-end BoP items craftable.
* Enchanting: Hard to level (disenchanting old gear instead of selling it), makes money at higher levels.
* Engineering: Hard to level (mats required not easily farmed), most items not usable by non-engineers, rarely makes money.
* Jewelcrafting: Hard to level (gems are not always easy to come by), makes money at higher levels.
* Leatherworking: Easy to level (when paired with skinning), makes money at all levels.
* Tailoring: Easy to level on the low end (farm coth from humanoids), hard to level at high levels (mats not easily farmable), makes money at high levels.

What professions go well together?

Fairly straightforward, but some are interesting.

* Alchemy & Herbalism: Herbs used to make potions via Alchemy.
* Blacksmithing & Mining: Ore & bars used to make items via Blacksmithing.
* Enchanting & Tailoring: Make items via Tailoring (cloth from humanoids) then disenchant it via Enchanting.
* Engineering & Mining: Ore & bars used to make items via Engineering.
* Jewelcrafting & Mining: Ore & bars as well as gems recieved via Prospecting used to make items via Jewelcrafting.
* Leatherworking & Skinning: Skins received from skinning used to make items via Leatherworking.
* Tailoring: No professions benefit Tailoring any more than another as cloth is received from humanoids. But Enchanting is often used to Disenchant items made from tailoring.

What can be made that is Bind on Pickup?

Some classes/specs/playstyles choose a profession to get a specific item. If you are searching for something specific from a profession, here's a link to tell you if you can have someone make it for you, or if you would have to make it yourself.

How do I unlearn a profession?

Any time you feel like you don't like the profession you have and you want to get rid of it all you have to do is hit the "k" button (or whatever else your hotkey is) to bring up the Skills sheet and look on it to find the skill you want to unlearn. Click it so that the details for it show up at the bottom of the screen. Look for the circle with the slash through it in the detailed section. That's the button you use to unlearn the profession. Click on it and you'll get this confirmation in the middle of your screen: "Do you want to unlearn Engineering?" "Unlearn" "Cancel" (Obviously it won't always say Engineering, just whatever profession you have selected.) Select "Unlearn" and you will have unlearned itl. You'll also see a message describing what you just did in your chat box.

Now you are free to go and learn a new profession. But remember that once you unlearn it, if you retake that profession, you have to level it up all over again.