privileges on tablespace

A newbie question :

I've just installed Oracle on my Linux box. I've granted right to create table to user Joe. However Joe is still unable to create his table since he has no privileges on tablespace.

Which tablespace should he use ?
How to give him privilege to modify the tablespace ?

Thank you,

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Jean-Paul Le Fèvre * CEA Saclay DAPNIA/SEI * Mail : Jean-Paul.LeFevre_at_cea.fr