a. PM a moderator if you'd like to update your listing. we have the ability to allow you to "re-edit" your post
b. if you're selling more than one thing in your thread... it's a good practice to update it once in a while, with the items that are still for sale and the items that have sold. that helps the buyer, the seller, and lets the moderation team know that there are still active listings for sale in the thread.
c. once something sells, it's very helpful if you can post "sold". then we know we can archive the thread... this ensures the people looking, are looking at valid sales, not expired sales.