If you are interested in someone, watch how they move through a crowded doorway.  Do they wait and hold the door for someone less mobile, or someone with their hands full?  Do they stride through and let the door swing, assuming that they who follow will catch it?  Do they look behind them to see if someone is following and could use the door held?  Do they stand in the doorway, unaware of people trying to come through?  Do they accept someone else holding the door for them, but express no thanks?  If a double door and someone holds it open for them, do they go through with thanks, or open the other door for themselves?

How they treat strangers is probably a good indication of how they will treat you.  Maybe not now, but eventually.

The Eroticist