Strengthening and healing one's auras should be done each day, in order to keep things running smoothly. This is especially true if you know that you're going to be in a stressful situation, or if you're going to be around emotional vampires or other negative folks who drain away your energy.
In order to protect your aura, the first thing to do is to put up a spiritual "stop sign" to protect yourself from outside energy interfering. One way to do this is to cross your arms and legs in a protective stance (or sitting position).
Then, you can try my friend's unusual breathing technique which is said to clear the aura and balance the chakras. With this cleansing, your auric area is cleansed and your mind-body connection is balanced. It is done by breathing in with one nostril, then out with the other.
First, hold your nose as if you're going underwater; just pinch it between your fingers, but don't apply any pressure. Close off one nostril and breathe out. Keep your tongue steady and low in the mouth, just behind the front teeth. Apply pressure to the other nostril while releasing the original one, and then breathe in for a few seconds. Hold the breath for 10-15 seconds if you can; otherwise, just do it for as long as you can. Then exhale, and do the same thing with the other nostril. Repeat the entire process half a dozen times or so. It shouldn't take longer than a couple of minutes.
I'm still learning about auric work, so I'm not sure how standard the above exercise is. However, one thing I can say about it is that with all of the concentrating on breath, it certainly can help to refocus your mind onto something new if you're worried or stressed. Breathing exercises are often quite calming and strengthening. I often do a similar breathing exercise without all of the nose pinching. Do what feels most comfortable for you.
As you're breathing, you can also try a "cleansing vortex" visualization. To do this, as you're breathing, visualize a swirling vortex of light, beginning in your midsection, and whirling outward and away from you, cleansing and healing your entire body, removing and dispeling all negativity that is embedded within. Imagine the negativity changing to positive energy, then visualize the whirlwind scattering this positive energy outward and away, releasing it into the general environment and doing good things for others.