Grant on table without access to other tables structure

Hi,

I will explain what I need with a simple example.

I have three tables:
jobs, people, cities

I have to grant select on people to john.

GRANT SELECT ON PEOPLE TO JOHN;

Now, when john opens "psql", it can do the selects. That is OK.

But when john does
\d
\d cities

He can see the other table names and structures...

How can I revoke this rights?

How can I create a new user and give him select rights on some tables,
but not disclosure the full database tables and fields?

PG is 8.3

Thanks,
Pedro