Most Helpful Girl
Invite him to a neutral place, don't tell him "you need to talk" because I hate it when people do that (not a reason not to use it but still). When you see him, don't talk around the issue. Let him know that maybe he noticed a change in your behaviour lately? If so (and even if not) tell him that's because there's a change in your feelings towards him too. That you feel more like friends than lovers and you don't think those feelings can come back. Tell him that you'd rather be friends than boyfriend/girlfriend and you feel he has the right to know instead of waiting to see if feelings change and you don't want to lead him on.