I guess you wouldn't really have to ask how to start a relationship if you were completely confident with the person you were talking to in my opinion, I do think this is something you should communicate to the other person about on a serious term in private.
You know when someone is in love with you, not by glances or a quick smirk, or a couple words - a devoted interested person is in love with you when they spend the time knowing your interests - they would mute out the world just to talk for hours with you and to communicate with you. And so that when they look at you sometimes, there's this shimmery glittering look in their eyes that makes you feel warm and safe. That's the difference.