Well, I'm a beginner -- but like most beginners I'm not going to let that stop me from giving advice. If you are having (as I was) difficulty holding the violin in place without gripping the neck, I would suggest that the first place that you should look is the shoulder rest. Assuming that you are placing the violin on your collar bone, with the end button against your neck and your jaw placed (fairly lightly without having to bend the neck much at all) on the chin rest, and you can't easily keep the violin in it's proper place, then there are two possibilities. 1. The shoulder rest is not properly adjusted, 2. You need a different type of shoulder rest and/or chin rest.

I'm on my third shoulder rest now, and the difference is amazing. I currently have the Bon Musica shoulder rest and I no longer have to use my left hand at all to support the violin. This allows the left hand, arm and shoulder to be perfectly relaxed while playing and is a major improvement. I only need a minimal amount of pressure from my head to keep the instrument firmly in place with my thumb lightly resting on the neck as it should be. The pro side of the Bon Musica rest is that it is highly configurable (by bending) to fit the exact contour of your body. The con side of the Bon Musica shoulder rest is that you have to configure it to the contour of your body, which takes a bit of trial and error. Once you get it right though it is great. Although, I have heard that is is not a good fit for those with short necks.

The Bon Musica looks like this: http://fiddlershop.com/accesso.....-rest.html

Incidentally, the Yehudi video was excellent and if you notice the large C that is formed by his hand keeping separation between the finger side of is hand and the neck, some have advised thinking of holding an invisible egg between your palm and the neck of the violin. Hope this helps -- good luck.