To increase your eBay sales:
1. You need to find very hot ( desirable products ) Thats very important to have great sales on ebay.
2. If you have good products but your competitors are selling more than you you need to focus of the quality of the images, description, shipping. At the most important - price. Also its good if your account is top rated + ( it receives more traffic from ebay, your listing are on first pages of the search )
Based on my experience the feedback is also very important. For example if I were a buyer I would buy the item from the seller with more feedback and more % positive feedback.