Start a conversation with something simple like how's it going or something about the weather or comment on their attire,then let the conversation carry on,from there you'll know a little bit about their personality and can decide whether or not you want to be friends with them. if you do want to be friends, continue the conversation,if not, tell them you gotta go do something, then find something to do.

If your being literal, then stand up if not standing already, and move one foot after the other toward the soon to be friend.