Too late for a lot of you pro staffers, but rookies like me can do this. I've written a short note - weather,location, time of day, decoy used and other information I want to refer to later on every bird I've killed. Sometimes a pattern will develope that surprises me. Besides that, it's a lot of fun to read in the off season.
I keep a journal of all my hunts. Helpful and great to bring back memories.