Brad and I always talk about what we need to work on to make our shows seem more fluid and professional. Some of the ideas are things I would not have thought of before I became leader/co-leader of my own trio (your mileage may vary):
Leave early to go to the gig in order to allow time for traffic or flat tire. Arrive early enough to set up and relax and become focused on the music before start time.
Keep breaks between sets to an agreed-upon length.
Minimum amount of time between songs: Finish a song, and count off the next one.
Come up with a set list in advance, and stick to it. Any problems with a set list can be discussed before the gig.
If a song is counted off at the wrong tempo, adjust immediately and play the song well at that tempo.