Are you talking about general love or love and sexuality? I think as far as just generally loving someone, most people know when that happens esp. because they put forth an effort to do that. If you love someone just because you have common tastes or similar interests like baseball or baking cookies that's not really love. Love doesn't have partiality.

The whole idea of "falling in love" is flawed from the start. Love requires both parties to put forth an effort to love the other person and express love through words and actions. It's true though that you can feel love for someone because of honorable traits such as courage or honesty or humility.

That's not to say that being sexually attracted to someone else is wrong, but that's not the basis of love at all. It shouldn't ever be the prime consideration in whether you love someone or whether you want to love someone. Relationships that recognise the attractiveness of the body as part of the character of another human being are superficial and will ultimately fail. It's irrelevant. It's an extra bonus that we really shouldn't put too much emphasis on.

The love we have for others should be the same way we would want to be loved. Deeply, sincerely, faithfully, willing to take sacrafices and spend time and energy to love another and show them you care. After all, it's greater to give than receive.

So I think instead of asking that question you should be asking these questions : What are honorable traits that I find lovable in another human being? What can I do to love another and grow a better relationship?

Hope that helps.