find the nearest public toilet -block the doors to stop anyone coming in,(desperate women can always brave the men's urinals) then sing the first two lines of the first song in your set, pronounce it a complete disaster and begin to change the set completely even though you have five minutes before the performance- then skip through the first line of the new songs in your revised set and then on the way back to the stage decide the original songs were better even though you cant remember which key they are supposed to be in - singing -we love it!