all the guitars are in tune, all the strings are new and rust-free, amp is positioned/mic-ed well with tubes that aren't about to burn out, spare amp as backup just in case they do, fresh batteries in the wireless, extension chords for the pedalboard, good cables, someone on standby to hand me guitars in case i need to do a guitar switch mid-set, stage monitor that i can hear.
and post-gig food. seriously, you need sustenance after a hard night of rocking to the max.