Secure Your Cable
This is one of the best tips you can get for playing live, it's really super important that you get into the habit of doing this ALL the time - I'd even recommend getting into doing it when you are sitting down to practice, just so it becomes the normal way to plug in.
One little note before you do this - if you don't have strap locks (you should have some, maybe I should have done that one first?) then be careful because the cable might push the strap off the button... I mean, it's unlikely but possible, so just go get some strap locks (See Quick Tip 3!).