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.

this is a UML question, and this is j2eelist not a proper place to ask your question

use sterotypes to define type of your classes  (entity, boundry, etc)
you may use package each for layers with layer  sterotype
you can some diagrams which show  relations between layers and subcomponents as package diagram.