First of all, don't panic. The Gameboy can smell panic a mile away. One main tactic is to keep as many options open as possible. Translation: What arrangement can accomodate the most possible tetrad shapes, and still complete lines?
In this fairly common example, placing the square against the lower wall will allow only a reverse-L or a straight tetrad to fit in the gap. However, if the square is placed against the higher wall, then an L tetrad can fit in addition to the other two. (Note the frustration the L tetrad feels otherwise.)