The best advice is to keep it simple. No one likes reading through a long add and will very quickly move on if your add is too long.
Make sure what you are giving away is in the title of your add and the first word. For example: Coffee Maker, good condition, not I have a good coffee maker. The first example is much easier for someone to spot than the second.
Use a picture if you can. Nothing attracts attention like a picture. Please remember that we expect pictures to be less that 100K.
Make sure you create your ad in the correct category.
When your item is gone, please log in to your account and mark the item as gone in the My active ads section. This is done by simply clicking on on the icon below the Sold heading.
That is it. Good luck giving away your items. Thank you for making your junk someones treasure.