locks

Hi all,

After almost one year using PostgreSQL, I'm still discovering things about
locks, we have little documentation about it:

I know that one can lock a table in the following ways:

* BEGIN statement:
If you don't explicit lock a table using LOCK statement, it will be
implicit locked only at first UPDATE, INSERT or DELETE operation.

* DECLARE statement:
Currently, PostgreSQL doesn't support READ ONLY cursors, once a cursor
is declared, other users can only read data referenced by cursor.
Write operations to the referenced table like UPDATE, INSERT,
DELETE or DROP aren't allowed until the end of transaction.

* LOCK statement:
LOCK don't allows read access to locked tables by the other users.
If another user try to SELECT a locked table, he must attend
until the locked table is released.

Just wondering if there are other ways to lock tables.
Any replay will be appreciate. Thanks, Jose'