(Based on a conversation that I had with my brother)
Leave your tip on the table.
As you are standing in line waiting to pay for your meal at the Diner, figure out what the tax will be. Give the cashier the check and exact change. As the cashier is totaling up the bill say, "keep the change."
Then you walk out.
The cashier will say, "hey wait!" before realizing that the total with tax equals the cash tendered. Then the cashier will say, "oh." After a moment's reflection, the cashier will realize that you are no longer in the restaurant and be very afraid.
The ninja customer: pay quickly and then fade into the night.
