If you're an altoholic like me, you pick and choose your professions to support each other. I've got 10 toons my my server and all but one have a 2nd profession. I was always wondering how other people leveled their professions. I really can't say I use a specific method as I just level as I need it.
Case in point was my paladin's Blacksmithing. Palladude was my 2nd level 85 toon. Mining was the easy part. Since ret sucked, I leveled as prot, pulling 3-4 mobs at a time and wearing them down. Kinda like tanking my own mini-instance. Loot, heal, repeat. Leveling that afforded me gear for my warrior and death knight as well. I don't do heroics too much, the ones I have actually finished were on toons with professions which did not allow me to roll on the orb (Engineering and JC). Kinda ticks me off but oh well.
Next thing I leveled was my JC on my shammy. Too easy I must say, especially with three miners on my account. I think this was the easiest one. I'm at like 527 and just buying patterns to fill in the blanks.
Leatherworking is a mo-fo to level up, but I have a plan which actually works. In the Vash starting area there are numerous crablike creatures. I use my 80 lock to pull and dps while my friend on his 80 rogue loots and skins. We both benefit in this fashon. I could farm faster on my 85 mage but I'd lose the leveling benefit.
Back to the question, how do YOU level your professions? Bit by bit? As you level? Or do you wait till you are 85 and pay through the nose for it?
On a good note, my rogue's engineering is 522 and my priest's inscription is 522...getting there!