One thing you need to remember about resturant work, the audience keeps changing, so the routines you choose should be ease of setup and simple in nature. Some people will come back in with others just because they enjoyed what you did and want to share their experience with their friends.
One trick that still amazes me with reactions is the Hot Rod.
http://www.penguinmagic.com/browse.php? ... ng=hot+rod
As far approching tables, if there is anything that advertises that you are doing magic, the 'intrusion' of the customers space is easier. You should learn how to read people so you understand if walking up to them will be welcome. If they seem to be in an intense conversation go on by. If you are doing some magic for others and others seem to be trying to see what you are doing, by all means, go over and do things for them when you are finished. When there is advertising about you doing magic (newspaper ads, tent cards, or even a sign as customers come in), sometimes people will ask the staff where you are and the staff can let you know where these interested people are seated. Also, DO NOT
be doing magic for the staff of the resturant while they are to be working if you too are working there (even on an off time). Management has a tendency to notice the customer care being neglected and people can loose jobs.
Learn some good impromtu effects that you can mix into your repertoire also for repeat customers.