- Date and time
- Gender of partner
- Where/how you met
- Your orgasm
- Their orgasm
- Toys used
- Specific activities like digital, anal or genital penetration, oral, kink, etc.
- Condom/birth control used
- A star rating for the encounter
- Alcohol or drugs consumed
Girly Juice's example spreadsheet is pretty thorough and interesting, so I suggest you go have a look at hers for some inpsiration.
The secret here is to be honest and truthful. There's no point in keeping data about yourself if you're going to lie to yourself. It's like trying to keep a food log but "forgetting" to put in all the snacks you eat. It might look good on paper, but it's useless for changing your habits.
Become a Sex Data Nerd
If you plan to have more and better sex in 2018, then keeping sex stats might be a great way to help you with that. Although we do know a lot about ourselves, we know less than we think. Noting your activities can remind you of things that you enjoy but forget to ask about, or of things that get in the way of having great sex (drinking too much, for example.)
Scientists use all kinds of data to understand the world around them. Psychologists have found ways to turn changeable human behavior into observable information, and keeping stats about your sex life is a little like doing a long-term self-study. What questions you have in the beginning and what conclusions you come to all depend on what you're interested in learning. Or maybe you're just interested in seeing where the data takes you with no specific goal. For the visually-minded, a cool project might be to make your own "sex infographic" summarizing your sex life for the year, for example.
Also, maybe keeping stats about your sex life will make it a less taboo topic for you, something to be proud of rather than ashamed about. It might also help you find more words to talk about your needs and desires, as well as what you like and what you don't.
Do you plan on trying this out in 2018? I already have my own spreadsheet ready...