the most important thing to know as a beginner is that the same problems that you're having right now - every one of us here have been through that. these are normal things, so don't get discouraged. stay with it.

most of the problems that you're having with making chords ring out is probably due to hand strength and positioning. Make sure you are pressing down on the string squarely to start. it may feel awkward but it will help you to keep from muting other strings...

lastly... practice, practice, practice...