i practiced for about four months on grass and ponds before even tying a fly onto my leader. it's a bit different when the fish start to rise or the water's flowing fast and cold, but i think the practice helped. i couldn't (still can't) afford casting lessons, so i took a freebie and the instructors liked my cast except for a small twist in the wrist which i've been watching. practice helps. now i'm back, landlocked from trout, and again practicing. trying to get good at longer, tighter casts so i can hunt reds on the coast.
i was lucky enough to get to fish some not-so-travelled areas in northwest colorado for three months so running into experienced anglers wasn't a big deal for me. if i did get a spot that was crowded, i'd either go elsewhere or wade as softly as possible. if i was alone and tripped and splashed, i only hurt my own chances. doh. sometimes, i think it's best to quietly watch experts fish a hole rather than try to fish the hole yourself if you're a relative newb like me.