<< Don't get a mean teacher (i hated all my mean teachers) but get one who is demanding for practice. Too many teachers I see only want students to practice 20-30 minutes, which is simply not enough.
Practicing anywhere from 1 -2 hours is necessary for you to become highly skilled. Consider that warm ups are usually 20-30 minutes, and each peice may last anywhere from 5-15 minutes to play. Oh, and practice playing blind folded (after you have played the peice a bit)...i found it really helps in the expression of the music. >>
Uh, to each his own I guess, but playing blind folded (in my opinion) doesn't help anything...
As for a mean teacher, demanding practice and what not, well, if you're serious about learning, your teacher's strictness will have nothing to do with it. Motivate yourself to practice.
And, Freebee, man I don't mean to rip on your advice or anything, but giving a number on this sort of thing is impossible. It's not how much time there is--it's what you do with it. There's always gonna be someone out there who practices half as much as you and is twice as good as you. So, it's all a matter of what you want to accomplish, and how long that takes you.