That's why you have a well worn checklist you use to start a jetliner. It's complex, so they wrote it down and that's how you do it to make sure you don't miss a step.

Reminds me of when I was showing my mom how to use a new piece of software and she opened a notebook and wrote it down step by step. That's how she starts her airliners. Now if only documentation was not considered an afterthought these days.