It is easier not to see love where there is only friendship or, simply, a desire of the other to be kind and attentive. Keep in mind that this interest in pleasing, known as social desirability, is innate to the human being and seeks to be accepted by the group.
When a man is flirting, he often seeks eye contact, smiles, and has an open posture towards the woman he is interested in. He leans toward her when he speaks, seeking physical contact, touching a shoulder or arm in communication.