Howtoforge posted a tutorial about upgrading from Ubuntu 11.10 to 12.04 LTS
The new Ubuntu 12.04 LTS (Precise Pangolin) has just been released. Ubuntu 12.04 LTS is a long-term support release, which means it is supported for five years. This guide shows how you can upgrade your Ubuntu 11.10 desktop and server installations to Ubuntu 12.04 LTS.How To Upgrade Ubuntu 11.10 (Oneiric Ocelot) To 12.04 LTS (Precise Pangolin) (Desktop Server)