when I start on a new lock - I picked it 10 times in each configuration up to 3 pins, then waited overnight - picked the 3 pins again 10 times and then moved on - the purpose of waiting overnight is that you don't rely on your memory of the pin hights as much.
really though, I just chose 10 times because it was a random nice looking number that sounded good at the time.
once you get up to the stage where all the pins are in the lock, change it arround every couple of days or so to keep you fresh - perhaps get a few practice locks and mount them -
try to practice picking them all within a certain time limit (pretend you're racing against the clock to save someone's life or something

) - this would probably involve raking or whatever's fastest.
also practice picking them so that you get to the stage where you can pick the lock first go using individual picking - lifting each pin only once and not having to restart - if you have to restart (by oversetting a pin and you're not able to reverse pick) then go onto a different lock and come back (pretend you've tripped an alarm or something to motivate yourself to do it right the first time)
anyway - that's just my way of practicing.
