So there is this guy I like.......?

This may sound silly..... but there is a guy I really like, he is a customer in the shop I run and he comes in quite often, he is always very chatty and a little flirty but I get the feeling thats just his nature. I cant tell if he likes me back for sure but my colleagues seem to think he does. I have never asked a guy out before and because he is a customer I dont want it to be all awkward if I ask and he says no.... so what to do??