I just look at the audience and say "I think they would like this", pick a style or Songbook entry and start playing.
I have a wide assortment of Songbook entries, many of which can be used for multiple songs.
There is a number of songs that almost always go over well, despite the makeup of the audience. I usually start with a few of those.
I'll switch genres until I stumble on something they like, then adjust from there.
No music, except some lyric/chords, either associated with Songbook or pulled up on the fly from kb or lt.
Probably 75 percent of the time I do everything from memory. I get a lot of requests, and sometimes it takes a few seconds to set up a style and/or chord/lyric file. As far as I know, I've never done the same set twice.