Have you tried simply introducing yourself ? Or complimenting his clothes - something like "wow those pants look great! Where did you get them?"
or "Don't I know you?" is always good. If you smoke, ask him if he has a cigarrette.
Ask him for gum.
Bump into him "accidentally". Not rough, just a nudge will do. Compliment his hair.
Say, "Don't you work down the street from me?" Whatever the answer to these questions, seem interested. If you can get a guy to talk about himself - and lets face it, most guys love to talk about themselves... they will be all yours.
Keep the conversation flowing by keeping eye contact, nodding and smiling, but keep away from talking about ex boyfriends or other guys. He'll just think you're not into him enough. Make it all about him, how he looks, smells, talks, dresses... and that's all it really takes. Show that you are interested in him.