Hold his eyes till he turns away, also blush if you can
The ONLY way it'll work, ...u MUST find a way to BREAK OUT of your SHYNESS & start a conversation with him
They probably like you anyway unless you reject them . Situations aren't perfect all the time ,right ? So you make a couple mistakes or you're awkward . There's a little leeway .And it depends what you want or what you're after . If it's just innocent flirting ( can't speak for myself , lousy flirter ) than you can learn as you go . but if you're looking for a boyfriend just be friendly and be yourself. I have such a hard time getting girls that it always amazes me when some girls admit to being awkward and shy too , I always assume girls are just born naturally confident in social situations
Look on the bright side. At least you can smile! I either give them a weird look, or look away immediately. Sometimes, I can't even tell if they're checking me out or not. But, to answer your question, try giving a flirtatious wink, and waving hello.
You can do what you are or you can make your life better, your choice.
Try taking your number to the cute guy the next time.
Just hand to him as you walk by, you do not have to say anything.
You have to stop caring what people think about you of you make a move. Just have fun with it :) life's to short to care about stuff like that