This reminds of a funny/sad story. One night after work a group of us took some visitors out to happy hour. Our office manager came along, who is Irish but spent many years living in Germany also. She paid the bill, and left before the rest of us. As the rest were filing out the waitress came up...
Bringing the check in a timely manner is important especially at lunch time. Also keep an eye out for groups where you know the check is going to be broken up and be prepared. Drop the check off before they're finished with their meals and be prepared to handle payment as soon as they are ready.
I read an article a while back on how to get better tips, IANAW though. I recall a few of the suggestions. Such as when you bring the bill, if you give out mints be sure and bring enough for everyone, or perhaps even two. I think it also suggested to give a few, then reach into your apron pocket...