hi!
here are some steps which you want to try:
1st: read the ejb3.0 and hibernate persistence specifications which can be found at the hibernate.org
2nd step: reverse engineer database tables. use the hibernate tools plugin for eclipse which supports ejb3 annotations. if you have a proper designed database-schema then the plugin recognizes the primary keys, foreign keys and their related associations. there are some ant tasks which do that for you, too. within this step you need to configure the connection to the database within a "hibernate-config-file". a reverse-engineering file could be useful. docu for all that features can be found under hibernate.org as mentioned.
3rd step: migrate the rest of your application using the right annotations.
xdoclet is not required any long when using ejb3.0 and hibernate.
hope that helps in some way.
best regards
patrik
ps.: a sample sourcecode can be found at
http://caveatemptor.hibernate.org