A searchable list of Frequently Asked Questions (FAQ) and the corresponding answers is available here: http://public.kitware.com/cgi-bin/paraviewfaq. This is the first place you should look if you have a question or encounter a problem.
The ParaView mailing list is the principal means of communication among users and developers. Please go to http://public.kitware.com/mailman/listinfo/paraview to subscribe to the list. Instructions are given to receive an archive version of the list; as well as to manage and unsubscribe from the list. Many developers and users of ParaView are subscribed to the list, so it is a good resource for questions that cannot be answered using the ParaView FAQ.
Commercial support is also available for ParaView. Contact Kitware at 518-373-4194 or kitware@kitware.com for more information.