Also signs telling people not to clap in church. We don't come to Mass to be entertained. Don't clap for the sermon, don't clap for the choir, don't clap for every little thing everyone in the parish does. DO take the time to personally compliment the priest on his sermon, the choir, people who do so much to make our parishes function if you feel so inclined. 

St. John XXIII said it isn't right for the servant to be applauded in his Master's house.