Sometimes it's hard to find the inspiration to create a unique work of art for a client. One thing that you can do to help open up your creative mind is to put yourself in the customer's shoes. What would persuade you (as a customer) to buy the service or product? Why are you buying it (is it a need or a want)? The one and only mission that a graphic design has is to sell the client's service or product (they act like visual salesmen). So if you can come up with an idea which would compel you (yourself) to buy, then you are definitely on the right track.
You can also look at how past graphic designers have dealt with similar products or services, and their creative work may spark some new ideas in you. Doodle design ideas over and over again until a solid design starts to show itself.
