I usually wind down with some yoga. This works because it helps me to calm down from the hectic nature of the day and lets my body know it’s time for bed.
Every night is a little different, and sometimes I stretch for half an hour while others I’ll just take some time to breathe in a few key poses. I try to listen to my body and see what I need at that particular moment.
If I’ve not yet done a wheel pose (urdhva dhanurasana), I definitely do a few of those (usually using the couch as a prop: I’ll drop to the seated portion of the couch and then walk my hands to the floor). Backbends can be quite energizing but I do them all the time so they don’t keep me awake; I’m usually up fairly late writing so this helps counteract hunching over my desk! I then usually follow that up with some kind of hip-targeting pose, whether pigeon (eka pada rajakapotasana) or bound angle (baddha konasana).