I started one two years ago and plan on continuing it through the indefinate future. It has location, # of deer and type of deer, date, weather conditions (cloud cover, wind speed, barametric pressure, percip.). I use excel and have been experimenting with formulas for predicting which stand to hunt for a given set of conditions based on the data from my past hunts...its the nerd in me I guess. I need a year or two more before I come to any conclusions about its accuracy but I like it so far.