i'm something of an airbrush snob. you'd never know it from my steadfast avoidance of them in my fett suit, but i've been airbrushing since the early 90s.
like everything, there isn't a right or wrong. everyone comes up with their own style over time.
a few things that are important to me:
i'll only use double action. WAY easier for me to control. i also only like bottom feed... the little cups at the top don't hold enough paint. with a bottom feed you can either use the little cup or bottles.
i've used:
paasche vl
http://www.dickblick.com/zz250/10/?wmcp=google&wmcid=products&wmckw=25010-0100-1515
classic brush. when airbrushing in the mall was big, this was what most of them had. my high school rig had a few of these. i didn't have the $$ for a big setup, but i had 3, usually one for black, one for white and one for colors.
badger anthem
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LX8157&P=FR
i love this one. i've got one currently. i've had it for years and haven't even changed a needle. though i don't do anything precise with it... it's all for laying down weathering / broad expanses of color where i want a fine gradient / no splatter.
iwata eclipse hp-bcs
i haven't used this one enough to comment. i had a 1/2 of any 1 item coupon for ac moore and it was the most expensive thing i could think of that i wanted
on the air source... i don't like the little always-on compressors that usually get sold at art supply stores.
right now i've got a porter-cable compressor from home depot. it goes up to 150 psi, and i paint at 30 - 40ish. it has a 6 gallon tank too, which is enough for 10 minutes or so of painting, and it refills fast. so basically the compressor is off more than it is on.
http://www.deltaportercable.com/Products/ProductDetail.aspx?ProductID=17019
it's LOUD though. i have a 50' heavy duty air hose that i plug the little airbrush hoses into, so the compressor lives far from where i actually paint.