Sight of the subtle which lies within and throughout all physical things comes with practice and concentration. Most of us can, to one degree or another, perceive the energy we manipulate, the life which courses through those around us. This is not so much something that is seen with the eyes as it is something which gives the impression of sight. It is a perception, an intuition, easily ignored or discounted. It may manifest to you as light or color as that is the easiest way your mind can interpret it. Whenever you attempt to see on this level, remember not to take the idea of sight too literally and instead trust your instincts and impressions.
Another sensual impression we gain is the sense of others' physical and emotional states. This involves our ability to pick up on their energy and latent thoughts. Though this can be done simply by focusing our attention briefly on the person in question, the strongest sensations are gained through physical contact. It is by gauging our impressions to our target's energy that we can determine whether he is sick or well, drugged, diseased, or intoxicated. We can further perceive his general emotional state, energy level, and level of power (if any).
Again, these impressions can be very vague and it will take time and practice to even realize that you can sense these things, let alone learn how to differentiate sick from well, energized from drained, and the diverse states in between. Learn through trial and error, as everyone's impressions tend to differ, and trust your instincts at all times.