via mobilebeat.com
This is a good checklist for your lighting setup. Just the idea of having any sort of checklist is always good anyhow, not just for lighting.
I like to keep a box prepacked full of emergency items. I keep all sorts of cables, adapters, zip ties, etc. Even spare mics.
Of course, any pro DJ will always have backups of EVERYTHING! Including backup speakers, amps, mixers, and most important – MUSIC!