text: The fact that you mostly see him at work, that is a great opportunity for you. Please don't be too forward with him - like asking him out on a date or telling him straight that you like him. He could be one of the guys that find it a turn-off. Instead try to show more interest in what he does at work, ask him "neutral" questions like: "What challenges are you currently facing here at work?", "What are your future dreams?" After about a month of chatting with him, start buying him lunch (but not too much) maybe once in two weeks, and say "I like this dish so much, I just thought of sharing with you." Be Creative ... good luck!