here are some tips for getting a higher score:
Tip #1: If you have a stone that you can't use at the moment, shoot them off into nowhere, rather than adding them into the line of stones, especially if you're close to losing.
Tip #2: If you create a gap between two stones of the same color, the entire line of stones will roll in reverse.
Tip #3: To tackle more difficult levels, focus on clearing balls near the front of the line and scoring chain bonuses, which results in filling up the Zuma meter faster (when full, you hear "Zuma!" and the balls roll backwards briefly)
source:http://blog.games.com/2009/09/18/three-killer-secrets-for-beating-zumas-revenge/