My general strategy has been trying to minimize mistakes instead of going for easy clears. if a piece will break and mess up something further down the slope, its not the best position even if it clears a line or block. also, i'm always trying to think in terms of how the pieces will fall and trying to set up combos in a way that's pretty similar to how you do chains and combos in any of the puyo puyo games. (this falls apart for me once the board gets too full or the pieces fall too fast though)