Hey there! The best practice system for using a pick is with a metronome (Period!). Practice 1/4, 1/8, 16th notes at a slow meter and increase as you get comfortable. If your attack is uneven or inconsistant you may as well not use one. Also, practice in "Playing Position" like you would at rehearsal or a gig. If you can pick like Chris Squire sitting down, it may not carry over when you stand up!
STORYTIME!
About a year ago I scrapped everything I knew about using a pick and started all over again. Although I had been using a pick for a while, I just felt I needed to rethink it and shake up my playing.
I went to the music store and bought 1 of every pick they had...all the sizes, weights, and shapes...they may give you a deal too because they think you are nuts..
I took them home and played along with some cover tunes my band does. I found 3 configurations of pick I like then tried them at rehersal. I now use either a Dunlop Ultex .73 (new technology pretty cool! Turning into my favorite), Fender Medium (cellulose - Personally found I could play the faster stuff easier but tears the thing to shreds!) or a Fender Heavy (the blue one).
Hope it helps.