There you are with your eyes locked on the eyes of your friend and vice versa. You've been observing the changes in your visual perception and verifying that each of you experience the changes at the same time, that the slowly cascading fluctuations in intensity are duplicated by each of you equally. The next step is to simply become aware of any strong emotional reactions you experience. Continue doing the visual exercise, but extend your awareness to include your body and theirs. Be alert for emotional sensation, and in a very short time you are likely to feel something. When you do, if both of you still have your attention locked on each other, both of you will experience the same emotion, at the same time and with the same level of intensity.
This is when you will begin to grasp the true nature of telepathic communication. Emotions are not simply sensations like rubbing your skin. They have characteristics containing information of a psychological nature. You can tell the difference between sadness and excitement, joy and longing. Emotions tell you something, without words, even without thought.
So consider what knowledge you gain about another person when you know what they're feeling, because you are feeling the same emotion. Until you experience sharing the same emotion, strongly, while doing this exercise, the idea of knowing another person's emotion may not seem so spectacular. After all, we can tell when someone is feeling sad or happy without telepathy. But when emotions happen to you and another at the same time, when you realize you are not simply "noticing" their emotions but sharing the same sensation, well, that's something altogether different. The boundaries separating the two of you emotionally disappear. You will both discover that the other knows you, for that brief moment, as intimately as you know yourself, at least as far as the experience of the emotion is concerned. Once the feeling is out in the open it is useless to deny it. You are responsible for allowing it to occur, and so is the other. Both of you know exactly what's going on. (The feeling of being in love with someone is very often a shared emotion, and most people "realize" this, though only at a subconscious level.)
Many people consider this "telepathy stuff" to be an infringement of personal space, and most of us have spent the majority of our lives "building walls" to protect ourselves from being emotionally recognized, except by our closest friends and family. The walls also help us avoid being caught up in the distress of others. The walls serve a purpose and most of us are loath to take them down without first developing immense trust in certain, favored people. You will find "mental etiquette" of supreme value here, and you will also find yourself assailed by everyone's most rigid walls if you don't tread lightly, often even if you do.
I can't count the number of times I've told someone what emotion they had just felt and had them deny it, only to say something later, after I've developed their trust, like, "It's difficult to be open with someone who knows your every emotion." I used to become irritated and doubt my ability when people would tell me, bluntly, that my guess concerning their emotion was wrong when my years of experience told me I must be right. Now that I no longer doubt the reality of my perceptions, I realize that I'm simply moving too fast when I get that reaction. Mental etiquette. . . it's valuable.