because you are not providing much detailed information your best bet would be J2EE core design patterns

books.google.ie/books+Core+design+patterns

however, one thing I'd like to say. because you are not using rich domain model  and entities apprently do not encapsulate any process you need to consider accessibility and deployment when layering your application. The more layers you add, more infrastructure you have to manage, logically or physically. I leave the detailed guidelines to the reference I mentioned above.