What do i do ????

I have a really big crush on this guy who works in my building (we don’t work for the same company) and I’ve never met a guy out of the bar (maybe reason I’m still single) so I don’t know what to do….like how do I approach him??? I mean we make small talk in the cafeteria and hallways but I don’t want to let him pass me by and I just don’t know what to do I’ve never been in this situation before….he makes me nervous and giddy and I just get flustered around him...i don't wanna ask him for coffee cuz if he shoots me down then it will be awkward, mind you the building is big enough for me to avoid him till we move offices in like a year but then again i guess its better than not knowing....i just havent felt like this in awhile...i dont know how to flirt sober !!!!