Waiters and waitresses: what do you want from restaurant patrons?

What specific advice can you give the rest of us so that we can make your jobs more pleasant? I’ve heard that working on wait staff can be pretty stressful. How can we avoid becoming a part of the problem?

Specifically: how much do you expect to be tipped? Is it any easier to enter things in if the tip itself or the total amount is an even dollar amount (or Euro, etc.), or does that not matter? Do you like for customers to ask for refills and such? Does that add to the stress, or does it make things easier? Would you rather just monitor the drink levels on your own? Do you feel cheated if a customer orders only water to drink? These are some specific things I wonder about, but I’d like to hear any other advice as well.