Start with a headline emphasizing the benefit the customer will get from your product or service. The body text of your ad should tell just a bit about your product, but should concentrate on the benefits your customer will receive. Personal benefits, not features, are why people buy products and services. End with your contact information, how prospects can either contact you for more information, or how they can order your product or service. Spice up your layout with a bit of graphic art.
Clip art is widely available at office supply and art stores.
It should be easy to find a book of art that will apply to what you are selling. Cut the selected art from the book and paste into your ad. Don't overdo the art, though. Use only one graphic at the most. More than one looks unprofessional.