This may seem obvious to many of you but there are so many servers who never think to do this. Make some room for your guests and clean off their table while they are dining.
Did I mention quicker table turnover? The less there is to clean, the quicker you can serve a new group of guests at that table. 😉
(This may not be appropriate at some fine dining restaurants, so if you work at one of these restaurants please disregard this tip.)