Writing a good description
Having a good description can be the difference between making the sale or not making the sale.
It's important to try and put yourself in the position of the kind of person you're trying to attract to your ad and ask yourself what information you'd like to see in the ad if you were the person looking to buy.
Short ads with little information rarely perform well while the most successful ads are the ones that include lots of information and descriptions and clear photo's which answer people's questions before they ask them.
It's important to include as much information as possible and include details such as shipping terms, costs, your returns policy if you have one, the total cost, when the buyer can expect to receive the item, if you provide tracking information etc.
Generally speaking, the more information the better as this helps the buyer make an informed decision without having to contact you for clarification on anything that you may have overlooked when creating your ad.