What Makes a Useful Facebook Page?
Post daily, talk about your products. Give links to a website and post pictures of products. Engage with customers and talk with them, answer any questions they may have and that will let them know you aren't all about profits. Happy customers lead to more sales, and more sales lead to profit.
Be Sure to Interact With Customers!
Make sure when looking in comments, if someone has a question, you take the time to answer it. Customer feedback is a cool thing and personally I think its cool when a company does so.
Post pictures and Videos, Help people to interact with your page and get to know your products