This is my bread and butter right here, I run a diy record label, and do short runs of vinyl, tapes, and cd-rs (
www.myspace.com/wolvesfightgoodrecords)
anyways
when i first started screening the physical cd-rs, and the covers for stuff. I went to an art supply store. asked them what I needed to get to get into screen printing stuff. and he set me in the right direction. I hate spending money on shit, but the only way to make sure a screen turns out good is to spend about 100 bucks, which if you're in a big city like me (chicago) you can do this pretty quickly.
I have been using the same 22x14 screen for the last 2 years, and have done LOTS of runs with it. well over 50, and I am just now getting to the point where I need a new screen. One screen can go a long way, you don't need a new one for each different design you do.
the best way to get your design on the screen is emulsion, I put 2-3 heaping spoonfulls on the screen and just wipe it down with the squeegee until its even. put it in a cardboard box and in a dark part of whereever im staying, and turn a fan on. it usually dries in about 3 hours.
Print out the design onto a transparency, and try to put a thin piece of glass between the screen and the transparency. this helps a lot suprisingly. idk why or how but it does.
then wash your screen out with one of the spray things from a kitchen sink, or a showerhead.
tape off the edges around the design so no ink bleeds where you don't want it to go.
as far as printing, it doesen't really matter HOW much ink you put on the screen, but try to put enough according to how many you are going to print, if I am going to do 500 7" record covers, I will put quite a bit on my screen. then go across once lightly to spread the ink over your printing surface (shirt, patch, etc etc) and then go once again and apply more pressure so the ink goes through to the shirt.
as far as cleaning the emulsion off the screen to reuse it, just go to a quarter carwash. this is the cheapist, and in m experience the best way.