Personally, these are the things I keep track of in my custom spreadsheet, for each wager:
-Today's Date (translated into whole numbers)
-My Pick
-Type of Sports (MLB, NBA, etc.)
-Posted Line
-Amount Risked ($)
-Units Risked (auto-calculated)
-Amount to Win (auto-calc)
-Book Used to Wager
-Result (W/L/T/Cancelled)
-Amount Won/Lost (auto-calc)
-Units Won/Lost (auto-calc)
-Total Bankroll to Date (auto-calc)
-Total Units to Date (auto-calc)
-Name of Handicapper (if someone other than myself)
-Any outside expenses aside from wagering (i.e. to purchase handicapping tools, etc.)
-Misc. Notes (if any)
Aside from these, I also keep a chart at the top of my screen that takes notes of daily records and automatically calculates the following:
-W/L percentage for all sports
-W/L percentage for each sport
-W/L percentage for each handicapper (incl. self) in all sports as well as in each sport
-Total money profit for all sports / each sport, minus any outside expenses
-Total unit profit for all sports / each sport
-Total outside expenses
Finally, I have a slot where I can input the "starting date" and "ending date" and all of the above records are re-calculated to reflect that time period. This feature is really helpful for me.
I think comprehensive recordkeeping is pivotal not only to making a profit in sports wagering, but to keeping your sanity and being able to look at things in perspective when on a losing streak. It also helps me weed out bad handicappers