Uhm...this is a tough one to answer. But I'm going to give it a try. First and foremost, there is no yardstick for measuring true love, or one working way to know it, but still that doesn't leave us clueless about what true love is or should be, or its attribute. That said, let me say before proceeding this is strictly my own opinion which doesn't bother on conventions around. That out of the way, the best way I feel is the most assured way of knowing true love is if there is an attraction towards the personality and not the person. When the object of interest is in the wonder of the personality and not the person. What this means is that there is major focus on the immaterial self than the material self. You are more interested in what that person is rather than who that person is. True love is known when affection is not instantaneously felt but built from the interest in the other person. In other words, true love is what you feel when you have a deep understanding of the wonders of the human nature, a process that is progressive. Hope I help?