I get tongue-tied and probably smile a lot, but I am relatively shy in real life, so I never went beyond that. I think my general demeanor is rather approachable, warm, and friendly, and so I always let them come to me when they were interested. That meant that if a guy didn't have the guts to pursue me, then I didn't ever get him, but it also meant that I didn't end up with a male who is spineless. ::shrug::
If the girl is particularly friendly with you - more so than with other guys - then you are probably safe in telling her you'd like to date her.
Come on, koolwhip! I know you can do it! The more you practice, the easier it gets. I swear. Be the captain of your ship, the king of your castle, the one who determines your own destiny!! Take a chance! You can do it!