This is a big change to what I normally put out on the site, but I am an Oracle DBA, so why not put some tips up for that as well, enough rambling.
This tip may help to overcome the problem where you have gone all through the screens, setting up the parameters, file locations etc for you new database, you are all ready to create the database, you click OK and nothing happens it just freezes.
This is incredibly frustrating, but the way I have got around this recently is, start the DBCA session again, go through all the screens as before, but as the end instead of saying create database, choose Save Template. Give your template a name, then exit DBCA.
If you navigate to $ORACLE_HOME/assistants/dbca/templates you will see the template you created.
Then from the command line enter (NOTE for this example my template is called test along with the global database name)
dbca -silent -createDatabase -templateName TEST.dbt -gdbName test
From there it will create and start your database for you, plus you have the template again if you need to setup the same database on another machine.
I am always interested in feedback so please feel free to add any comments, or you can mail me here. If you would like to submit a quick tip with full credit and links back to your site then also feel free to contact me.