Worked at a Denny's about 40 years ago. Letting people know you are behind them is very important. Back out through the swinging door if carrying anything. Always look busy. When I started, the manager told me even if there is nothing to do, grab a rag and wipe something down, take empty glass racks back or tidy them up. Never just stand around. If you are again, people can really get you. We had a busboy/dishwasher that let it be known from day one that he didn't't want to be there. He was locked in the freezer for a few minutes a few time when no manager was around.