Yep, first tip will look like a bit retarded, but taking off on your board won't be any easier in the water that it is in your living room. So don't be affraid to look like a kook while nobody is looking at you and practice on a dry floor with fins on your feet. Be sure your knee and front foot land each time where you want them to land.
After you're confident you can take off and drop the knee, practice it a lot. Especially when waves are not so good. Even if the wave closes out, make the drop and start a bottom turn. It won't make the wave, but it will teach you a thing or two in the process. If you want to improve take not so good days as good opportunities to improve.
For practicing turns, better to choose a not too fast and not too hollow wave first, with easy take off, as you will want to have a lot of opportunities to turn.