Tags and tagclouds are all over the web nowadays. Almost every blog or website has it. Setting up a tagging system in Drupal is very easy. If you are using Drupal as a weblog, this might be a great feature for your website. Heck, it is a great feature even if you're not using Drupal as blog.
Here I will point out some things that should be done by yourself after you have installed Drupal. It's a basic Drupal site configuration - some things that I always do when I create new Drupal website.