The 'Bleeding Love' singer - who was recently romantically linked to One Direction hunk Liam Payne - admits she used to be shy about approaching guys and could only tell them how she felt by writing down her feelings, reported Contactmusic.
Giving advice about relationships, Leona said, "If he's talking about you to a mutual friend, even something as simple as asking where you live it shows he might not yet be confident enough to approach you himself, but knows your friend will feed back to you.
"I used to write letters to guys I liked rather than approach them directly because I was too embarrassed."
Lewis also recommends looking for eye contact with a man as one of the best ways of knowing if they are interested.
"Just like us girls, guys are programmed to send out physical clues when they're interested in you, and this is usually the first sign that he's into you. If your crush isn't someone you know well, lingering eye contact and a smile are signs to watch out for. They're a good hint that he's really attracted to you."