Make Drills Count!
Focus on what you are doing-
Concentrate on the skill you are trying to perfect. It will payoff.
Don't just go through the motions-
Few things will improve your swimming as much as just really trying hard.
Take it seriously-
Drills are often seen as fun or a point in practice to mess around and talk, but improving your technique should be top of your list. Yardage helps you build endurance, but better technique will actually make you faster.
Unless your coach says otherwise, drill work should be done slowly and methodically. Never race while doing drills.