1. Try to find the Tabernacle. Look everywhere, even in closets if at first its location is not clearly obvious.
2. If you're not sure what you are looking at is actually a Tabernacle, see if there is a red lamp beside it.
3. Look for statues, but keep in mind their absence does not necessarily mean the Church is not Catholic.
4. Try to locate the stations of the cross. Be sure to look on the floor if there are none on the walls.
5. Are there Holy Water fonts? If it is Lent they may be filled with sticks or stones or even sand, so keep this is mind as you begin your search.
6. Look for the choir loft. If there is none, or if it is empty, and you see a stage near the sanctuary, you are probably in a Catholic Church.
7. Look for the altar table. Check to make sure it is plain and bare of adornment.
8. Do the silence test. If there is none, it's a safe bet you are in a Catholic Church.
9. Listen to the choir. If there is no plainchant, and what comes out of their mouths is liturgical pablum, I'm sorry to say that you are probably in a Catholic Church.
10. And the easiest way of all to tell you are in a Catholic Church? Everyone goes up to receive Communion!