Can you pick a lock that has had some pins removed? Like a 2 or 3 pin lock? If so, then there is really no different technique in the others. Practice on a really simple, easy lock until you can open it easily. Then progress to a slightly more difficult one.
You didn't mention what locks you were trying to practice on. It is very possible that you have been scrubbing away at a lock with security pins.
If you are limited on funds, go get a Master Lock #3 padlock. they are fairly easy to open. If you've got about $15 USD then get yourself a cheap deadbolt lock and do the pin removal and practice on it. You could even change the pins around once you've mastered it and you'll have a "new" lock to pick (although the picking order might be the same, the depths will be different).
Don't stop practicing on a lock once you've opened it once or twice. Keep at it until you can open it with ease, then move on.
As for help on your technique, no way to really know what it is you might be doing wrong but the most common problem is too much tension. This is especially true when raking.
If you're aiming to be able to pick random locks you may be presented with by friends or co-workers to see your magic skills, then you need to practice on a lot of different locks. Go back and forth. Don't assume that because you've picked it 20 times that next week you'll be able to just pick it up and open it with ease again. For me anyway, I tend to learn a lock and go through the motions that I remember from opening it so many times rather than actually feeling it out and unlocking it's puzzle. I have about 25 locks or so and I bounce from one to the next.
Ok, now I'm rambling.... hope that helped.
