Beginners: Hit colors, dodge spikes (greys). Hit power blocks inside corkscrew loops for bonus points.

Advanced play: Your main goal should be to collect matches only when the puzzle grid is as full as possible. So it's sometimes advantageous to avoid color blocks and even to hit spikes (Hitting spikes erases one puzzle block. Hitting spikes also resets the match timer, just like hitting color blocks does). Look to intentionally hit spikes especially when a corkscrew loop power block is coming soon since your bonus points will be based on how full your puzzle grid is.