How do I keep visitors out of my blog admin area?

Question from one of my Blogging 101 students:

I visited my blog URL ( http://myusername.wordpress.com) it takes me to my blog but allows me into the administration dashboard of my blog.  How do I prevent visitors from getting into that?

Answer:

If you mean that it let’s you see the admin login area allowing you into the Dashboard, that’s because you have saved your login information (your probably checked the “Remember Me” option) in your browser when you first logged into the wp-admin page.  That will only happen from your machine. Your visitors should not see it.  Try your URL from a different machine and you’ll see what I mean.