Good naming practice. Either pull each line of non-trivial code out into it's own method, or assign the output of the code to a variable that tells you what it's doing.

If you find yourself repeating an assignment, pull it out into a function and remove the duplication.

Rinse and repeat until everything in the file is assigned to a descriptive function or variable. Doing this with someone else's code gives you a feel for how to do it with your own.