We understand that data migration can be a challenging aspect, and we've provided an ant-task to help you in this.
Use the build-sql task we've provided in DemoSite/site/build.xml to generate the current schema. Use the same task on your previous version, and then compare the deltas, which will tell you what is new and what needs to move. You can then build your migration scripts with ease.
Edit: Another way to handle seeing the deltas is starting up your application pointing to a copy of the old database with the hbm2dll set to update with hibernate logging turned to INFO. This will actually generate the necessary update statements for you instead of having you do it yourself!
Alternatively, you could use a database change management tool like http://www.liquibase.org/
Your last option (not recommended) is to leave the Hibernate autoddl setting to "update" for production, which will cause the application to create the necessary new tables. For example, if you added a field to Order that is only necessary for new orders, you'd be ok to do it this way. However, this won't help you if you need to manually move data around.