How to just flirt with him?

Coming straight to point there is a boy in my office whom I like a lot,he is my senior.I like him so much and I know he also likes me too.He is famous for flirting with girls outside the office (not office girls) I just want to spend some good moments with him ..he also likes me and he often signals me by smiling and behaving very nicely with me,appraising my beauty,my clothes,my perfume etc etc.But as he is my senior and a very rude person in the office ,im little bit afraid of him or you can say its my 1st time so i have no experience how to start flirt,how to make him feel special .I also dont want to hurt my ego and i remain want to b innocent in his eyes.what to do?