Start with a descriptive title. The title is what will catch your buyer.
Ex. If you are selling a car, include year, make, model in the title.
If you are selling a dog, include type of dog, age.
In the description include necessary information.
Ex. You may want to include years and condition.
If you are not a registered user or do not include your email address when submitting your ad, make sure your contact information is included in the description.
If you are negotiable on your price, state this in your description.
In the description you can also include which side of town you live on.
Photos are a key part to selling your item. Showing clean, clear images of what your selling may be more attention grabbing than your copy.