Everything I have up to the return line works just fine. However, when I try to add a button to turn on an LED, things go haywire. How do I include the button to go onto the next set of commands? (Turn the LED on. Later I will have the commands for the crane itself.)
There is not a need to call exit() at the end of loop(). All of your introductory display information should be in setup() since you want to run it once. Everything you want to run again and again is put inside loop().