Make one design and use it for lots of products - for example, the same design might work well on invitations as well as business cards, envelopes, and cards
Design with a specific customer in mind
Design something you would want to own or wear
What Not To Do
Place a large square photo on t-shirts
Apply a design to 50 different types of t-shirts
Put your design on products where it doesn't belong
Use copyrighted or trademarked artwork or phrases without permission of the rights holder.