easiest way is to go out for a couple of drinks with the person first in a group setting then gradually just the two of you and start spending alone time then it will happen if it is meant to happen.
But it all depends on what kind of person your boss is, whether he is already interested in you, or if he is married, in which case, it wasn't meant to happen.
Going out for drinks in public with others is good, but you can be coy and do other things too like drop hints, and maybe a back/shoulder rub, sitting on the desk might help with a short skirt (but no fat thighs) if he is a guy, but that might be a bit cliche.