Cheech, I don't have a template (but that gives me an idea)-
What I do is jot down the date, meat, type of cut and the weight of it. Then I list my preparation details-which rub I uses, if I brined or not and the type of brine. What smoker I used and what type of wood(s) used for smoke. What type of mop I used and when I started mopping and how often. I also note the weather conditions (hot, cold, wet, dry, wind-no wind) my starting time and finishing time and finishing temperature.
I also list the relevant comments and suggestion my guests makes as well as my own observations-like if I need to add or reduce something to my rub or pull the meat sooner or leave it in longer. And I'll also down any ideas that I might want to try the next time.
I hope this gives you some idea of what to put down. Remember it is your journal and you can make it as simple or as detailed as you like.