Best way is really to just tell the guy you're not interested. If you don't want to tell him directly, leave him a voicemail and tell him that you're not interested in seeing him or make it casual like saying your not in a place to start a relationship or you're seeing someone else. This guy could just really like you (I can see why) and really be interested in you and if you let him down easy he'll likely go away. If not, the Jman approach should be used
WG