Debu Panda's blog on theserverside has a good summary of J2EE Classloading Best Practices. This applies to any large J2EE application, not just Oracle (OC4J) applications.
The list has obviously come from hard experience, with examples of how to get resources and and work with common API's.
The comments on hot deployment are very container specific. Different container vendors make different mistakes/assumptions when it comes to redeployment.