I have been called 3X.
It depends on if you are going to a City or County court, and how busy a courtroom it is. If you weren't going in already, I'd say try to put it off as long as possible (you can usually claim hardship and put it off for a few months - if I had heeded that advice, I would have moved before I actually had to serve).
Bring something to keep you busy (reading material, game boy) and realize that it could be a day (if you or your case gets dismissed right away), or it could be a week or longer (my dad was stuck as foreman on a jury for 6 weeks.)
It's.. interesting, but it can also suck.