Play Air Guitar When Needed
When you mess up (which is normal) and you don't know were your at just pretend to play.
This tip works really well when you're playing in front of a audience. The reason why this works so well is because when you give that ''uh oh'' look it looks really obvious that you messed up. Your audience will not even know that you messed up when you pretend to play because they don't even know all the music. So you can play it completely different and nobody will even know.
But this does not mean you have to pretend all the time. The best tip of all is to practice every single day. You can never have too much practice.