Block placement: protect a useful empty corner
Inspect all three pieces before placing one. A good move leaves somewhere for the awkward piece as well as the easy one.
Find the anchor square
The selected piece extends right and down from the square you choose. Every square must fit inside the board and remain empty.
Clear lines without isolating holes
A full row or column clears. Filling a line while leaving scattered single holes can make the next large piece impossible.
Check every remaining piece
The run ends when no remaining piece fits. Use smaller pieces to create a line clear before committing a large one.