I save the scorecard after the first time I play a course*, and then replace it when I get a new personal best. The rest of them find the trash, after comparing them to the personal best scorecard. That's about it. Not very sophisticated, yet I always seem to know (or at least think that I know) what to work on. I am sure this is not the best way, but I play golf for fun.... I do keep meticulous notes on my swing though!

* First time I play a course, I do make an attempt to figure out what clubs to hit, and make notes of that on the scorecard.