Lets talk set lists. They are important people. Dont ever try to do one of those shows where you just "wing it". and I'll tell you why.
Heres what happens. . You can never remember all the songs you know when your on stage, and the problem comes inbetween songs. The easiest way to look unproffesional and like you dont have a clue in the world is to have "dead air" or even worse, mindless babbling banter than nobody but your band understands.
Nobody wants to hear you go.. "Hey Al, what should we do next".. and Al says.. "I don't know Geff.. what do you think we should do?". Nobody cares, they didn't come there to see you try to figure out your show as you go. A solid band knows where they are going. Now that's not to say you cant do the occasional request from time to time.. but just make sure it doesnt take you ten minutes to figure it out. Realistically you should be able to go from one song to the next within a matter of seconds. Practice this, its important. Nothing like having a dance floor full of people, and they are all waiting to keep rockin, and your standing there talking to your buddy. It just doesn't go over well.
The other thing about your set list is you need to manage your tunes. In what order will they go over the best? Do you want slow songs mixed with fast ones? Which songs will go over best towards the beginning of the night, and which ones should you save for later? Which song will best start out your night and showcase your talent appropriately? All very important factors to discuss with the bandmates when planning out your list.