It's as simple as taking your eyes out of focus to see the aura. If you've ever been able to see those holographic picture-in-a-picture things with your eyes, you shouldn't have any trouble seeing auras.
When this topic initially came up during a conference, I had little luck viewing the auras of the other attendees. That night, I went to the bookstore and bought a number of holograph picture books, which I sat with until my eyes could rest and I could see them. I had no issue seeing the auras of the other attendees the next day when I returned for the remainder of the lecture.
Stand in front of a light-colored wall in a dimly lit room with your training partner. Place one finger in front of your partner's chin, about 6 inches away.
Now, instead of looking at their face, fix your gaze on their finger. Remove their fingers while keeping their gaze fixed on the same area. This will require some eye relaxation. Now, if you stare at them with the same relaxed vision, you should be able to see what appears to be a small line running all around them a few inches away from their body.
The following layer out is considerably more faint, and it may be colored. Depending on who you're talking to, the distinct meanings of the colors can be rather different. In this case, my recommendation is to expand your awareness and see for yourself which colors appear to be related with specific types of individuals and actions the most frequently.
Experiment a little with this. When they think positive ideas, does their aura change? Are you having a bad day? Feelings of rage?
Some people are born with the ability to see auras, while others must train themselves to do so. If it takes a long, don't be too disappointed. You'll progressively become aware of increasingly more delicate levels of energy surrounding people as you work with this. You may also discover that you can sense another person's chakras and even determine which chakra is their dominant one, which can instantly tell you how that person would react to any particular stimulus.