There will always be rattles, all you can do is adjust the clamps as tightly as possible and turn up the stereo.
One thing I've noticed is that when I stored my car with the top off, it would fit much more snugly when I did put it on and rattle less. When it's left on the car all the time it rattles more--take it off for a while and put it back on and the rattles aren't nearly as bad.
Squeaks can be attacked with some clear silicone grease.