Newbie Emergency #1: "I'm locked out!"
If you log out without having set up a convenient login block to let you back in... you're locked out! Right?
Fortunately, there's an easy way back in: <your domain>/user (as in, www.yoursite.com/user) will always provide you a login form. (A site that doesn't have "clean URLs" enabled needs to use <your domain>/?q=user instead; try that if the above doesn't work.)
Yep, I've done the Locked-Out Panic. So have countless others; it's THE emergency de rigeur among Drupal initiates. Get a Drupal tattoo to mark the rite of passage, then log in and carry on!