I suggest practicing with a flower first. A fresh cut flower or house plant usually has a nice bright aura, and you can get some distance from it so that you are not straining your eyes. Auras are energy, and once you can see the energy of one thing you can see the energy of anything (including spirits, other auras and your own magick).
Meditate just before hand so that you are relaxed. Don't try hard. The harder you try, the less you'll see. Gaze as you would when scrying, don't stare. When you see it don't tense up or get excited. Remain calm and continue focusing and you'll begin to see even more. The longer you do this, the clearer it will get. The minute your eyes start feeling tired, stop, because you won't make any progress with strained eyes.
Background doesn't really matter. Some say white is best, but the one factor I find most important is lighting. Dimmer light is best, especially candlelight or a lamp with a good shade in the room. I can see energy and its color and shape very well, but in direct sunlight or a super bright room, I can only see outlines and I have to really try to see those outlines.
My theory is energy creates its own light (since it is not tangible it cannot reflect light wavelengths) which is why most people see spirits at night. It isn't that they come out only at night *enter spookie music* it's that the dark and quiet calmness makes it easier to notice them. =)