My thoughts;
The first thing I think of in terms of a "great gig" is all members showing up on time, in the right frame of mind , ready to work with a positive attitude.
If you've had a bad week, an argument with your spouse or family members, leave that stuff behind until your back home.
Everyone should be on the same page. Your there to entertain and have fun and hopefully help out in creating a fun atmosphere for the whole band.
That's where I start, I have other criteria for a great gig I'll share later.
Blue