I saw this guy coming but I was facing the sun. I let him pass me and then said “hello”. This made him swing around to see who was talking to him and the rest is history.
Many times street photographers have to come up with all sorts of tricks to get the photo they are looking for. It does take a certain amount of nerve to do something like this but it is a lot easier than what you might think it is. Best case scenario, the subject is going to smile or laugh at you. Worst case scenario, the subject is going to insist that you delete the photo, no problem, you simply delete and move on.