Obviously even popular and successful restaurants have problems related to losing money.  Many estimate how many servings they would like to have on any given day.  And sometimes they can have issues with customers staying longer than the restaurant would like...not freeing up tables.  An easy way to alleviate some of this: offer customers a subtle and tasty incentive to help them move on.  Give each individual a free treat; not a typical restaurants after meal indulgence, but something special and highly sought-after at your restaurant (i.e.-some exceptionally delicious cookies, candy, pastries, etc.), that is only given with the check.  Change these regularly, and don't inform customers what's being served (the mystery adds even more interest); just tell them it's your restaurants "going away gift". This will not work all the time (and this is not asking them to leave), but having the check at the table, along with your restaurants departing treat, will certainly help move some people out the door.