Last time I played out (about my 2nd time ever in a proper club), I turned up with my record bag all arranged with the tunes I wanted to start off with at the front all the way to the back with what I wanted to finish on... First tune in the bag was jump up 'cos I pre-empted what the crowd was like... Got there and the guy before me played a bit of jump up, then went into Racing Green by High Contrast and the place went MENTAL. Cocked up my planned set. Fortunately I had a good mix of tunes and he had a few that I knew so I borrowed them, and I played mostly liquid/jungly stuff for the whole of my set, despite bringing down a bag mostly full of jump up and darker style tunes.
My lesson learned was: Next time take twice as many records as you need to do the set and cover all the styles that you play... At the end of the day there is no telling what the crowd will be like on the night so be prepared.
As my old man would say: Prior Planning & Preparation Prevents Piss Poor Performance