The most important thing? (Though now quite in the vein of your query.) RECORDS! RECORDS! RECORDS!
Once you start playing with a few different bullets styles/bullet weights/sabots/powders/powder weights/primers, etc., your memory goes south. Write it all down and hang on to it. Sometimes you see a pattern starting to show up that will lead you in the right direction. At the very least you'll avoid repeating things that didn't work.