When we had the band in NY our theme song was "Where or When" which I had picked (I did most of the song selections for the group) the lyrics just seemed to fit ... nowadays, it depends on the venue: restaurant/Country Club I will most often start with bossas and my go to tune is "Blue Bossa" ...
For Assisted Living/NH gigs, I set up a playlist, usually centered on some theme, and pick from there ...
Summer/outdoor gig, it is definitely something to get their attention ...