First, use the square you have the most duplicates of since you aren’t constrained yet. Thereafter, avoid using any unique squares (qty 1) that you don’t have a duplicate of, unless you can win with it.

If able, try to preserve your tiles that have your two colors opposite each other, or at least try not to run out of those tiles before depleting those with your colors adjacent - running out of any variety of tile lowers your options.

You can see which squares your opponent has (in parenthetical red font under your quantities). Use this information to make moves your opponent can’t counter due to his shortage of critical square types.

It is advantageous to place your color so that you match your opponents adjacent color - thus closing the square and denying your opponent one score.