As a seller on eBay, your item description is vital to whether or not your item sells and the final price that the item goes for.  Here are a few tips on writing an auction description:

• ALWAYS tell the truth!  If an item has a dent, scratch, hole, tear, etc., you should always state that in the description.  Your reputation is everything.  Lots and lots of items that are sold on eBay are used and that's okay.  There is nothing worst that a buyer winning an item that is not in the condition that the description implied.
• Be complete.  For example, if you are selling clothing, be sure to list all of the measurements.  It is easy for a potential bidder to decide against buying because a piece of crucial information was left out.  It can also cause you to get a ton of emails with questions.
• Use keywords in your title and description.  Most browsers will find your item via searching on eBay.  To ensure your item comes up, always use the best possible keywords.  This will make your listing easy to find.  For example, if you are selling a new green Moonlight Care Bear, a good title to use would be: "Cute Green Moonlight Care Bear - New" instead of "Great Green Teddy Bear for Your Kid."   When writing your title keep in mind that there is a 45 character maximum - so make the most of your space!
• Clearly state your payment terms.  If you require payment within 7 days, be sure to state it.  If you don't accept credit cards, be sure to state it.  It you neglect to mention something now, it will be hard to hold a bidder to it later.

Also be sure to check out some of our other articles:

Best Times to End an Auction
Leaving Feedback After the Auction
Starting Your Online Auctions Business