For your first question: Talk to kreia once you're level 15+ and strongly aligned to one side of the force(very LS or very DS). One conversation is all that you need.
For the second question: It is very difficult, if not impossible, to turn all to jedis in one playthrough. Take a few of them now and others next time.
The key is influence, you must gain influence and say the right things. I think you need to talk to a twilek on Nar shadaa for Atton, and you must take Mira to Nar shadaa too. But always, it is influence that matters.
Oh, and those who can be turned are Mira, Bao-dur, handmaiden, atton, disciple.