I believe one of the most over-looked parts of an Auction is the item description. If you take a look at the items people are selling, they always leave you wanting to know more.
It seems people either can't be bothered or they think that having a picture will do all the selling for them.
In my opinion, if you take a little extra time to write a thorough description of the item, you not only provide people with all the information they may need to make a decision to bid on an item, but you most definitely are putting your item on another playing field from similar items others are selling, as you are providing more details.
A good place to start with your description is a brief but thorough description of what the item does. Then comes the history of the item, if you bought it new, how long you've had it. How much work the item has performed, or the usage of the item.
The most important part I believe is to mention any defects or wear and tear, or faults the item may have. If you leave this out, you run the risk of potential bidders either overlooking your item, or once they receive they item if they are the successful bidders to make complaints or leave negative feedback.
Just remember, that "Honesty is the best policy!" It's true!