A huge part of Tetris Attack and its descendants is performing chain reactions of clears. That's when you you clear three or more blocks, and the ones that fall clear some more.

But I have trouble thinking far enough ahead, especially once the pile starts rising quickly or in a heated battle, to set up more than one chain in a row, so I use something called Skill Chains. Skill Chains are chain reactions that you set up on the fly, usually while the previous clear is... erm... clearing.

For example, take this puzzle and clear the stars in the vertical column in the middle

And while those are clearing, move that triangle in the bottom-right corner two columns to the left

For an instant 2-chain!

This is actually much easier to show in animated .gif form, so you can do that here (2MB file warning, dial-up users).

You can extend these as long as you can find the correct blocks to do them with, and with enough practice this essential skill will become second nature.

Good luck!