This one might seem trivial, but I start cleaning by picking up the floor first. This makes it easier to move around, which is a prerequisite for almost every other task.
How bad does the situation have to be that picking up stuff from the ground enables you to move freely?
It's the same thing in a codebase. If your functions mutate arguments, even a little, or if the code is not formatted consistently, the resistance to movement increases, and tasks become less pleasant. If you wait for real spaghetti code it's already too late; if you're used to chaotic code, you won't understand what I'm talking about.