One of the reasons I have so many alts, (one of them being that I can't make up my mind about anything, ever) is that I love having all the professions maxed out.
I absolutely despise having to sit around and wait for someone to craft me something, or having to buy it off the auction house when I can make it myself. Having a lot of free time on my hands, I have the luxury of being able to farm all the things. Not that it's particularly fun, though it sometimes is, but I prefer farming mats over spending money on it.
With the new expansion coming, I had to stop and think about how to organize my professions on the new server. My boyfriend Mad and I have moved a character each already, and since I can't possibly transfer all of my characters over, I've picked two more that will be shipped there as well in the next couple of weeks. How did I pick those? Well based on their professions of course.
Mage : alchemist / tailor
Hunter : enchanter / jewelcrafter
Druid : scribe / herbalist
The fact that they are my three favourite characters had something to do with this, as well.
So in the next few weeks, I have to level mining to 525 so I can start farming ores as soon as possible when MoP is released and level jewecrafting. I also want to level skinning so I can eventually help Mad level leatherworking. Since I've already created two characters on the new server, a paladin and a shaman, I'm thinking maybe I will take mining/blacksmithing on one and skinning/leatherworking on the other.
And if I'm lucky, Mad will take engineering on his rogue and save me the trouble of having to take it myself.
As for secondary professions, all my characters get maxed out on first aid, cooking and fishing at some point, but as far as archaeology goes, my mage is the only character that will ever max it out. Because I'm an altoholic, but I'm not masochistic. While fishing isn't that much more fun than archaeology, at least I can sit somewhere and never move.
Plus, I'd be devastated if I got one of the mounts on an alt.