From what I've read in the posts, much of what I have to add has already been said.

I never lean off the bike when I am on the street. When I started riding on the track, the instructors had us leaning off the bike in order to achieve correct body positioning. The idea was to move your entire body to one side of the bike. I was instructed that the best way to to this was to shift one butt cheek off the inside of the bike and then drop your elbow at turn in remembering, of course, to look down the track through the corner. This puts your entire body off the bike and keeps your upper body from staying over the tank and center of the bike which would be counterproductive.

Done correctly, you can't help but putting your knee out. The idea is to allow faster corner speed with less lean angle. The bike will accelerate better (read safer) whith less lean angle. Hence keeping the bike as upright as possible will allow for greater acceleration out of the turn.

My instructors never stressed actually getting a knee on the ground; but when I did what they suggested, I soon found that my knee actually does drag along the ground.

Interestingly for me there is a difference in right as opposed to left turns. While turning right, I get a knee on the ground. Going left I think I come very close but don't actually get the knee down.

I agree with other members that , if you are doing this on the road, you are probably going faster than you should be.