1) create the destination you want the MBean to listen to. You can do this in e.g. in jbossmq-destination-service.xml found in deploys/jms
2) Create your Bean class
3) write the ejb-jar.xml (you will find examples on the net)
4) write the jboss sepcific deployment descriptor, called jboss.xml. Here you define to which destination your MDB should listen to. You find the dtd in docs/dtd
5) Create a jar which contains:
5.1) Your bean classes
5.2) A directory called META-INF. Put all descriptors in this directory.
6) Put the jar in JBoss deploys direcory.