Let’s assume that you’re in a relationship with this dragon.
Depends on the dragon, but most will get flustered by you doing cute stuff. You’re a tiny, cute little human, and they love you. So flustering them would be very easy.
Just telling them that you love them would get them huffing and looking the other way because oh b o y you’re too sweet for them.
But if you smooch them? Dead. You’ve flustered them too much. Just a little smooch on the snout or the cheek and they’re completely done for.
Or you could just shower them in compliments. Most people don’t say such nice things about dragons, so just, compliment away.
You could also just cuddle up to them after a long day and pet them, tell them how much you love them, how great they are, how much you care about them. They’ll be super flustered, even if they won’t admit it.