Best practices for page layouts
Panels is a great module, but it can also be complex and it can take a while before you completely understand it. If you're interested in using panels for every page, the Panels Everywhere module is an interesting project.

Another great project that provides more flexible layouts is Display Suite.

Although people tend to use either Panels or DS, they are not competitors. They can be even used together as you can read on the blog of the author/maintainer of DS: Using panels on view modes in Drupal 7.