Operate your boat at normal cruising speed, trimmed to desired position.  Turn your boat to the left and then to the right, and note which way it turns the easiest.

If adjustment is needed, loosen trim tab bolt and make small adjustments.  If the boat turns more easily to the left, move the trailering edge of the trim tab to the left.  If the boat turns more easily to the right, move the trailering edge of the trim tab to the right.  Retighten bolt and lake test.

TMD