There are lots of kinds of concerts. First of all, you have to find out what's going on.
Most newspapers publish listings and advertisements for upcoming concerts.
Check the Sunday paper for a list of the week's concerts. Sometimes the Thursday or Friday paper will have a list of weekend events. If you listen to a classical or public radio station, you're familiar with their announcements of upcoming events. Sometimes a station will play recordings of music that will be heard in concert. Call your local station and ask them when you can hear information about live concerts.