Depends on the show Drew. More complicated shows generally have time to program, and its just like Elation_Pro said, someone hitting 'Go'. Sometimes, it is linked to time code, so no one is even hitting go. Cruise ships are a good example, all the shows run off of time code, and the show starts when the sound guy hits play.
The fun shows are the ones you have no idea what you are getting into. It is even more fun with movers. Running movers on the fly is often called busking. More powerful consoles like the Hog 3 or Grand Ma have full blown effects engines in them to make busking an easier task. They also have unlimited cue lists so you can run many scenes and/or cues at once.
The other big thing is if the console is tracking or cue-only. Makes a huge difference in how you can run your show.
Long story short, there isn't a standard way. Depends on the show, your console, your school of thought, time involved, and a few other things. There are shows in which I can program yet choose to run on the fly for more effect. There are some shows that I program part of the show and run the other part on the fly. Then there are shows in which I program the whole thing. I even did a dance concert in which the show had a 40 minute long dance piece, and I program the console to run itself. Meaning I program follow times in every cue so I only had to hit 'Go' once and that was it. So figure out what works for you and your situation the best and go with it.