Not sure if I've used the right flair, first post on here :)

I (20F) had fleeting eye contact with a cute guy the other day in a restaurant. I was with friends, he was with friends. Nothing came of it, but it's been on my mind since because I'm starved of intimacy and obsessed with romance.

I noticed him noticing me, so I'd like to think he was checking me out but maybe it was just an accidental glance.

My question is, in an ideal world (where he was interested), how would I give him the go-ahead? I'm 100% too shy to approach but how could I hint that I'd like him to approach? Is a smile all it takes?