WordPress MU

I have searched around forums regarding the issue of "private posts" and "private categories" and got a little bit confused.

Basically, what I want to achieve is to have an easy way to make some posts private and visible only to the blog owner once logged-in. I found some plug-ins, then in other sites these plugins were mentioned as already integrated into WPMU. In fact, I installed couple of plugins (like privatepost.php or ds_private_blog.php) but did not get the desired effect of easy "private posts".

So what are the best ways to create private posts or private category?

thanks in advance,
Ggreg