1. Get adequate sleep.
Late Saturday nights are Sunday morning's worst enemy. Resolve to turn in earlier. A good night's sleep on Friday night is equally important to waking rested on Sunday, as sleep debt builds up over time.
2. Drink plenty of water, though not too much.
It is easier to remain alert when you are well hydrated. Consider keeping a small bottle of water with you during worship. One quick bathroom break is considered permissible. Two or more are bad form.
3. Eat a high-protein breakfast.
Foods high in carbohydrates force your body to metabolize them into sugars, which can make you drowsy. If your diet allows, eat foods high in protein instead, such as scrambled eggs with bacon.
4. Arrive early and find the coffee pot.
If you don't drink coffee, consider a caffeinated soda.
5. Focus on your posture.
Sit up straight with your feet planted firmly on the floor. Avoid slouching, as this encourages sleepiness. Good posture will promote an alert bearing and assist in paying attention, so you'll get more out of worship.
6. If you have difficulty focusing on the service, divert your attention. Occupy your mind, not your hands.
Look around the worship space for visual stimuli. Keep your mind active in this way while continuing to listen.
7. Stay alert by flexing muscle groups in a pattern.
Clench toes and feet; flex calf muscles, thighs, glutei, abdomen, hands, arms, chest, and shoulders. Repeat. Avoid shaking, rocking, or other movements that attract undue attention.*
8. If all else fails, consider pinching yourself.
Dig your nails into the fleshy part of your arm or leg, pinch yourself, bite down on your tongue with moderate pressue. Try not to cry out.
*consider that you may be providing visual stimuli (see #6) for another patron in which case it is okay to continue.