I've been called up several times, but have never served on an actual jury. In NY, one frequently gets called as a so-called "standby juror" which only requires you to call in the night before to see if you need to report to the central jury pool each day for five days (in some counties it may be longer). If you call and your summons number isn't listed, then you don't have to do anything for the next day (other than call in again the next evening). If your number does get called, then you have to go to the central jury pool the next day. Groups of jurors for voir dire are drawn from the central jury pool. If you don't get called to voir dire on two consecutive days, then your jury duty is finished for that round, and you won't be called again for at least two years.
If you do get called to voir dire, then you might end up getting seated on a jury, if you're not disqualified. If you get picked, then you serve on that jury until the case is done; if you get disqualified, you go back to the central jury pool and wait to see if you get called again. If you don't, then after the second day, you're done for at least two years, as above.
There are very few exceptions to jury duty service now. It used to be that a substantial number of people could automatically get excluded, like lawyers, but that's no longer the case.