January 24th, 2016 29,298
Upgrading to a minor version is done through the upgrade process of Debian. For major versions, the process is much more complex.
A guide to upgrade a server machine from Debian 7 Wheezy to 8 Jessie using apt-get. Remember to create a full backup before.
Dedicated server setup, using Debian 8 Jessie step by step. It is a Hetzner EX40 server. Apache, php, MySQL, memcached. Basic monitoring and security tools.