One thing I do is after making a game or two I go through my projects and think about what was easy to work with and what was a pain to work with as far as my scripts go. I strip out the stuff specific to the project in those scripts and put them in an empty project that is ready to go for the next game. For the scripts that were a problem, I spend some time researching new ways to achieve whatever the script was supposed to do. Usually doing that ahead of time before I start a new project.