Years ago I read an interview with a musician (whose name escapes me), where he was giving advice to new musicians. There was lots of good stuff, but the one that really stuck with me was this.
Save your best songs for the encore, even if you never get the chance to play them.
At the time, this struck me as very odd. However, over the years I have started to see where this guy was going. The first thing is that all your songs should be good – if you rely on one or two and the rest are fillers, people will notice. If you are so confident in your songs that you can leave the ones you feel are best for a potentially never heard encore, you are on to a winner!