If your arrangement appears ongoing, it's best to establish some ground rules. Ask some or all of these questions of yourself and your partner: Is this actually casual for both of us? What happens if our feelings change? How often and when do you want this to happen? Do you expect a date beforehand? Are you cool that I'm also seeing other people? Is this a secret from friends and coworkers? Have you been tested? Do you like it when I put it there? How does that feel? Do you mind getting on top this time? Really? Right now? In the kitchen?