Please tell me what to do!!! I need to know!!!?

So I like my best guy friend, but I don't know if he knows. We tease each other all the time and tell each other we love each other and he has seen me at my best and my worst and I have only known him for a little more than a year. I don't want to risk losing my friendship with him though. So should I subtly flirt with him? like not a lot because I don't want to overwhelm him. And how should I flirt?