I came up with this idea years ago, and it never stops being funny to think about. For this trick, you will need heavy metal, dark, "creepy" clothes, and an assistant.
1. Put on the creepiest, gothiest/bikerest stuff you own. Remember, you want to look menacing and "Satanic" (for certain definitions of the word Satanic).
2. Get a pair of over-the-head headphones, and turn up your metal music loud enough that you can hear it just fine with the headphones hanging around your neck. This step is optional, but adds to the effect.
3. Get your friend and go to the nearest Christian bookstore. Leave accomplice in the parking lot and walk in, acting as if you're just on a regular shopping trip and it is perfectly normal for you to be there. For best results, accomplice should be visible from inside the store.
4. If they haven't thrown you out yet, go up to the cashier and ask, "Do you have any books on exorcisms? My friend and I kinda had a little accident." Cue accomplice pretending to have a seizure in the car.