You should average around 30, 35 is pretty high to expect. To get better mileage:
-Make sure your tires are properly inflated, not too high or too low, although too high is better than too low.
-Clean air filter, or better yet, a K&N filter.
-Keep up on your oil changes (clean oil reduces friction) and keep an eye on your oil level and don't let it get too low, Honda's tend to burn more oil than other engines, especially if you drive hard.
-Drive sane....shift around 3-3.5K, don't speed excessivley on the highway, drive you car in as low a gear as possible without bogging the engine.
-A tune up could help, go with NGK plugs and wires, it's the oem replacement brand for Integra's.