Hi marganda
When I joined a meditation circle at a spiritual church, the leader always made sure we 'closed' ourselves before leaving the building. She said we can feel rather 'floaty' if not...and as most of us were driving home, it wouldn't do to be 'floaty' when needing to concentrate on the road.
Imagining roots from your feet going into the ground (earth) is a good one. If I remember correctly, the leader used butterfly wings for the group. We imagined our wings closing in around us and making us safe. It also meant we were no longer open to other-worldly experiences for the time being.
And afterwards, give yourself time to readjust to the physical world. Take it slowly, open your eyes gently, do a few stretches and deep breaths. You could even stamp your feet on the ground. She encouraged us to stay an extra 10 minutes, have a cup of tea, a biscuit and a chat.
Squatch