Ive got a Korg DT10 floor tuner and Ive managed to mute myself in the middle of songs by inadvertently treading on it. I was going to start using the mute button on my amp and running the tuner through the tuner-out or using the bypass, but now Ive read of mute button disasters Im not sure its a better idea!
Here are my tips some of these Ive learned from watching other bands, one or two have happened to me : )
Take enough spare batteries for your effects, or if you use a 9v adapter get a spare!
Get a screwdriver with replacement heads that fit any screws youre likely to need to adjust. Using the wrong screwdrivers will quickly strip the heads from screws and then you wont be able to replace the batteries you remembered to bring
Always have 2 leads for each application that you know work properly (speaker leads for your cabs, instrument leads, patch leads, amp power leads) then you can lend one to your guitarists if he forgets his he will do this.
If you have a spare bass, take it with you, even if its a cheapy no name bass you will need it one day! (probably when the batteries in your 18v active bass die and youve only got one replacement battery)
Take enough spare batteries!
Dont stand immediately to the right of left handed guitarist on stage (assuming youre right handed) one of you will end up with a broken nose or, worse, a broken headstock.
Dont switch your amp off after youve sound checked if youve never noticed how long it takes for your amp to come on you certainly will if your band is waiting for it before they can start the first song
Did I mention taking spare batteries?
Ive written down 2 lists of equipment. One is all of the things that go into my flight case (pedals, leads etc) the other is a list of larger equipment (cabs, basses etc). I then use the lists to make sure Ive loaded everything into the car - Ive only started doing this recently because a bassist who headlined a gig in our town had a 3 hour drive up from London to fetch his amp head
I also found it useful to learn how to set up the other band members equipment, but this is only because when our guitarist has technical problems he just pulls a sad face

and says something isnt working
Hope that helps someone someday
Jamie