BUBBLE ZUP is a game of patience.
Wait for the bubbles to line up so you hit more that one at a time.
Try to keep your Percentage high and your BURST count even higher!
Full Disclosure: the BUBBLE ZUP concept and code are based on this excellent tutorial by Eoin McGrath: http://www.smashingmagazine.com/2012/10/design-your-own-mobile-game/