Not acting needy is huge. Simply don't change your behavior from how you acted before you slept together. That's really the key. If he's not interested, then he's not interested. But if he is, becoming needy, insecure and desperate will kill that.
You can't keep his interest if there was none to begin with. Just wait a few days and see if he contacts you and is interested in seeing you again.
Keep being affectionate, don't play games.
Kissing just for 1-2 seconds, hugging for 1-2 seconds, holding hands, kissing on cheeks, sprinkle drops from your wet hair after bath, true love never decreases mans interest .. instead increases... these may help..
Can't say perfectly... but a warm nude hug their itself with the gals head on guys chest is a good option after sex.