How create common tables?

I have Oracle 9i enterprise.
I've been creating a db and other objects (users, workspaces, roles, profiles,...), but I don' t know how I can create a set of common tables where all the users I've had created can work.

At the moment, if I creat a table in a user squeme, and other users want to access to this table, they have to put first the user's name.

Example:

select * from user.table

What I want is to avoid that, and only type:

select * from table

And that, for an user group defined by me.

In this form, all the users could work in the same tables.

Sorry for my speech.

-- 
Rosa Mª Sánchez Garrido