It really depends on how thick and bold you want your ink to be on the shirt. plastisol ink, unlike discharge and waterbased ink, does not dye the garment, it simply wraps itself around the fibers. therefore you have to decide on the type of print you want to produce. if you want a very light soft print i would go with a 230 mesh sceen. it wont allow too much ink through even if you put too much pressure on the squeegee. you can also buy additives that soften up plastisol ink. if you want a more bold print that is completely opague i would use a 110 mesh screen. that will allow alot of ink to go through the screen with each pass.