Auras are essentially just the energy that surrounds a person.
People often say that they have different colors. These colors will vary depending on the person, their personality, their current mood, and even what they are doing at the moment that you examine it. For example, I have always found that the color generally depends on their personality and then how vibrant it appears depends mostly on mood.
So if a person is happy or confident, the shade will appear very bright, whereas if they are nervous it may be very muted. If they are in a very negative mood, I have often found that the aura appears to be rimmed in a darker shade.
If a person is public speaking and uncomfortable or nervous, that will affect their aura just the same as doing something they love.
It takes a bit of practice to see them, but for me, I always start with meditation. I plant my feet against the ground, and sit in an open position (this just means that you don't sit with your limbs crossed over yourself too much. It is believed that doing so would close off the energy or tangle it). I close my eyes and feel my own energy running through me and spreading around me and focus on my connection to the Earth.
When I feel connected to the energy around me enough, (for me, this is a sort of cozy feeling, calm and warm) I open my eyes and look for the auras of the people around me. It helps if you don't focus your eyes straight on them but stare at a point near them and use your peripheral vision to see the energy around them. This is just because our eyes are very accustomed to focusing on what is easiest to see, so you have to sort of trick yourself at first. (Similar to if you have ever seen waves of heat rising from blacktop. They are harder to see when you stare directly at them.)
This is the way I started out with it. With more practice, you will have an easier time seeing them, and they will appear more distinctly.
Just a note, inanimate objects can appear to have auras too. They are just not based so much on the object as much as who uses/has been using it. For instance, the pencil I most use for writing would reflect the energy I give off while using it. Energy can be sort of sticky that way, in that it attaches itself to things both through repetition and strength (if I use the same pencil often, or use a pencil once while giving off very strong energy).
