I started about 5 years ago. I keep it on a day planner. I put down where I went, with whom I went, what the river conditions were, what the tide was for salt water or tide-affected areas, what the weather was like, what we fished with, what we caught fish on, and any unusual, noteworthy thing that happened. Also jot down if I observed anything new or different being used successfully and notes about what to try out just forget next time, if anything like that made a real impression.

I also keep notes about places I read about and how and how far ahead to make arrangements to fish. All kinds of things. Like was mentioned above, it's amazing how just a few lines will bring back memories that would otherwise be lost. It's just fun.