Whats in your bag of tricks?

I make a lot of rules or tricks for myself when doing different projects. Things I keep in the back of my mind to stay consistent, or just keep things straight in my mind. When I was writing “Alone” I had to keep the twin characters straight and not confuse myself about which one was which. My solution was to name the right side twin (they were conjoined at the head) was named Randolf and the Left side twin was Luis. I would love to hear what tricks or tips you use.