What profession is best for you?

Every character has two professions, and has many options to choose from for these two options. Almost every profession provides the character with something that the character can use that others without the profession cannot, giving a little bit of an advantage to the user. Of course, there's other advantages than what I have listed here, such as farming, selling crafted goods on AH, and fun, to think about. But here's what knowing each profession can do for you:

Alchemy

Alchemy's big buff is that all flasks last twice as long then normal, as long as the alchemist know how to make those flasks.

That being said, sometimes while the advantage is nice, it always a matter of getting mats for every hour-long flask. Alchemists also have the Alchemist's stones, although I don't think they're all that helpful in a raid.

Blacksmiths

Blacksmiths have the utility to be able to open up most locks with various keys they can make, the top one being the Titanium Skeleton Key. But that's just a side item.

Blacksmiths can also socket their bracers and their gloves. The socket they make for belts can be used by anyone, but these two extra gem slots can fit any non-meta gem in them. That could mean another +48 Stamina, +38 Spell Power, +32 Agility, or the buffs from two of whatever gems you want to add.

Enchanting

The big buff that enchanters get all for themselves is the ability to enchant rings, and two rings means two extra enchants. Here is what they can do:

• Enchant Ring - Stamina
• Enchant Ring - Assault
• Enchant Ring - Greater SpellPower

So that's +48 stamina, +64 AP, or +38 Spellpower. About the same as blacksmithing, but more limited.

Engineering

I'm an engineer, and i have a blast with it. It has a few fun things that I enjoy using from time to time, but in most boss fights it isn't that helpful. Since our GM has the Traveler's Tundra Mammoth and we're in Ulduar, my repairbotting is on break, but it still comes in handy every once in a while. We also have a mailbox, and a few things we can enchant ("tinker") our gear with. While most mainstream enchants seem to trump these, I do have a Personal Electromagnetic Pulse Generator (which does stack with my extra belt gem). I dont use it that much, but it helps with the Deconstructor.
I can enchant my cloak with slowfall and +15 agility, but that's 6 less than I can get from enchanter, for example.

Herbalism

Herbalists make some money and get Lifeblood. Nice free bonus heal.

Tailoring

Tailors have some cloak enchants that have a chance on hit/attack/cast to give either +300 AP for 15 seconds, +250 SP for 15 seconds, or grants 300 mana. Tailors also have spells to embroider spellthread onto pants using only a Eternium Thread, but these are the same enchants that usually take more mats that anyone can use.

Skinning

Master of Anatomy: +32 crit rating

Mining

Toughness: +50 stamina.

Leatherworking

For leatherworkers, its all about the cuffs. They have a couple special Leg reinforcements for their own gear, but it is only the same buff as those they can make for everyone in the game, just with less materials. They can give the following buffs on their wrists:

• +60 Resistance to one of the 5 schools.
  
• +114 Attack Power (64 more than the highest enchant available to everyone, +50 AP).
  
• +67 Spell Power (37 more than the highest enchant available to everyone, +30 SP).
  
• +90 Stamina (50 more than the highest enchant available to everyone, +40 Stamina).

Jewelcrafting

Jewelcrafting provides some blue-quality socketed trinkets, each with two sockets. More importantly, though they get to craft Dragon's Eyes, and they can use up to three of those Dragon's Eye gems. These provide buffed versions of all the other gems available for any slot. The total bonus makes Jewelcrafting about equal to everything else, except with more flexability in how you want to buff yourself:
Each Dragon's Eye can give you:

• +27 strength, agility, parry rating, armor penetration, resilience, expertise, haste, hit rating, crit rating, spirit, dodge rating, or defense rating.
• +54 Attack Power
• +11 Mp5
• +32 Spell Power
• +41 Stamina
• +35 Spell Penetration

Here's link to the list of Dragon's Eyes, as I don't want to link all of those individually.
All of those that give +27 are the special versions of a regular gem that could give anyone +16 to that same stat. This results in an extra +33 for these stats. For example, I could use 3 Delicate Scarlet Rubies for a total of +48 Agility, or I can use 3 Delicate Dragon's Eyes for a total of +81 Agility, or 33 more than normal.
For stamina, I could get +41 for each Eye instead of +27 for each Sky Sapphire, giving me +17 extra per Eye, or +51 extra stamina.

Edit: (thanks for the tip, Saruto) Dragon's Eyes are also prismatic, which means that they count toward any color you need for your requirements of a meta gem- this can be very helpful, for example, for mages who need to fill 2 blue slots but don't want to give up pure spellpower.

Inscription

The bonus for Scribes comes mostly from buffed up Shoulder Enchants. They also have a utility of having an extra hearth every 20 minutes, which could be helpful at times. They produce some epic off-hand frills, but my uneducated guess is that they can be quickly replaced by gear from raids, just like the Engineer's goggles.
The shoulder enchants are where it is at though. They are similar to those you can get from the Sons of Hodir:

• Master's Inscription of the Axe gives +104 Attack power and +15 Crit, which is 64 more AP than Greater Inscription of the Axe
• Master's Inscription of the Crag gives +61 Spell power and 6 Mp5, +37 SP than Greater Inscription of the Crag
• Master's Inscription of the Pinnacleis +51 Dodge rating and +15 Defense rating, 31 more than Greater Inscription of the Pinnacle
• Master's Inscription of the Storm gives +61 Spell Power and +15 Crit, +37 more SP than Greater Inscription of the Storm

There we go, that's all the professions. Here's a summary of the buffs you can get from the various professions, comparing a stat for tanks, for physical damage, and for spell damage/healing:

Profession	Tanks	Physical	Magical
Alchemy	?	?	?
Blacksmithing	2 extra defensive gems	2 extra Attack Power, Strength, or Agility Gems	2 extra Intellect or Spell Power gems
Enchanting	+48 Stamina	64 Attack Power	38 Spell Power
Engineering	Blue quality trinkets with +84 Stamina	Lower Epic Bow, Epic Helms (lower quality than most Raid Epics)	Epic Helms, fun bombs.
Herbalism	2000 self-heal over 5 sec, 3 minute cooldown	2000 self-heal over 5 sec, 3 minute cooldown	2000 self-heal over 5 sec, 3 minute cooldown
Tailoring	chance on use for 300 AP for 15 sec (nothing to buff stamina or defenses)	chance on use for 300 AP for 15 sec	chance on use for 250 SP for 15sec, or to return 300 Mana
Skinning	+32 crit rating	+32 crit rating	+32 crit rating
Mining	+50 Stamina	+50 Stamina	+50 Stamina
Leatherworking	50 more stamina than usual bracer enchant	64 more attack power than usual bracer enchant	37 more spell powerthan usual bracer enchant
Jewelcrafting	+51 Stamina, or +33 of most other defensive stats	+33 agility, +33 strength, or +66 Attack Power	+39 Spell Power, +11 Mp5, +33 Intellect, or +33 Spirit
Inscription	31 more dodge rating than usual shoulder enchant	64 more attack power than usual shoulder enchant	37 more spell power than usual shoulder enchant

So most of these are fairly even (You can get 48-54 +Stamina from Blacksmithing, Mining, Leatherworking, Enchanting, or Jewelcraftin).

So now that that's done, I should remind you all that your professions are also for fun. Choose what suits you best, or what you have most fun with. After all, this is JUST a game, right? ;-)