Walk past and make eye contact and smile. If he returns the eye contact and smiles back at you, then you’re most probably in for a great time. You can stop and have a quick quiet chat in the corridor or just head straight for a private room or other area.
Another hint: walk into a room and make it obvious you want him to follow you (wink wink …). If he follows, it’s on!
Remember, No Means No! If he doesn’t show interest or says no, then move on. There are plenty of other men around. Don’t hassle a guy by following them endlessly. You wouldn’t want someone doing it to you, so don’t do it to others.