I have been playing for almost 6 years now and I realized that one of the biggest things that slows me down is that my palm usually touches or rests on the back of the neck. This is a bad habit I developed since I taught myself guitar for the first year and a half of my playing. When I finally got a guitar teacher, he tried to correct it. To some extent my hand positioning did improve, but I still suffer from the same issue of finding it difficult to move up and down the neck, usually having to force my hand to move. It's playing this way since the resistance from my palm requires me to use more force to change positions. At first I never really noticed, but now it frustrates me because I have located the source of my problem, but am having a hard time fixing it.

I noticed that a lot of players keep their palm away from the neck and usually only have their thumb and fingers on the neck. I want to change the way I hold my guitar in order to improve my playing, but I am finding it difficult. Perhaps if you have gone through this before (or if you haven't) could you give me any advice?
I used to grab the neck of the guitar as well. When I got an instructor, he noticed this within 5 min and corrected this. At times I go back to chocking the neck, but I notice quickly and go back to using proper form.

Only thing I can suggest is keep at it. It will take time, but it will become second nature to you.
My guitar teacher suggested that there should be enough room between your palm and the neck to hold a hamster. If the hamster is dead after you have finished playing then you're doing something wrong... But a dead hamster might help your palm slide I suppose... Give it a try?