We regularly see the same questions pop up on the mailing list or on our irc channel. While we try to write documentation on how to do all these things, some things might be easier to explain using a quick example. I have recently created screencast for two such issues.
Debugging your Drools application in Eclipse
The Drools Eclipse plugin contains various debug views that allow you to do advanced debugging of your Drools application, showing the object in your session, the agenda, etc. Check out section 7.10 of the Drools Expert documentation. This screencast shows you how to get these debug views working for a simple Hello World rule. It also shows how to use breakpoints inside a rule.
Domain-specific nodes in Drools Flow
Drools Flow allows you to create your own domain-specific nodes. Such nodes have their own icon, properties and possibly even a custom editor. This screencast shows how you can create your custom work item node, use it in your process, and then register a handler to execute it at runtime.