My first question for you is, why? Why do you want to sell your item on an Internet Auction? There can be a number of answers to this question. It could be just for the thrill of watching people lust after something you have. If that's the case, I can give you the number and name of a few psychiatrists. That's the wrong reason. Good reasons are: 1) you can get more for your item on the Internet than at your neighborhood flea market, 2) it takes less time and trouble, 3) it saves on commissions compared to local auctions.
Next you want to look at where you're going to advertise your item. Which auction site are you going to use? First, before you do anything else- KNOW YOUR AUCTION SITE. Know how much they charge: do you pay a flat rate, commission, or both? Check out the site's reliability and reputation.
When considering a site, you also want to consider how easy it is to use, can you upload a photo of the item, and what are their security measures. How do you know if the person bidding on your site is dependable and reputable? Twice while I was selling items on auctions, the person who won the bid did not follow through with their purchase. Find out if you are you out the advertising money even if someone does not follow through with their bid (once the auction is over)?