No, there is no way, converesely we guys have no way to tell if a cute smile is just friendly or a signal that she's nervous around us because she likes us.
The good news is, you don't need to be able to tell.
When a guy flirts with you, or you think he is flirting with a romantic intention, all you have to do is flirt back and see how he reacts because any Christian guy will know it's on him to ask you out and if he doesn't it's either because he is just a friendly guy who flirts for fun, or it's that he just lacks the confidence to take that chance.
You could help him out and make the move, but it is important to remember that if a guy can't get over the first hurdle of asking you for a date, then is he going to be capable of leading the relationship that might develop?
That is a judgement call only you can make, as the person who knows his manner and character etc......
So just flirt back, give him a week, or however long you consider reasonable to build up some confidence, and if nothing happens, just forget aboout it.