Written by Xmodem(#freebsd@undernet)

You should actually not do it the quick and dirty way without
thinking and you should study the process to know what implications 
upgrading your OS might have. The handbook has more vital information 
regarding that matter.

Consider the following issues before continuing below:

- Multiple users on your box are changing things using binaries that
  are being replaced, same applies to certain services

- There are many available tuning options or configuration files you want
  to check out or modify (e.g. make.conf, supfile, filesystems)

- Specially, upgrading installed ports is a delicious matter, since you
  originally might have compiled some with specific options; use portupgrade
  but use it with care (e.g. upgrade one port after another) and study its
  command line options

- If you break your system that way and come to IRC whining about it, the 
  FreeBSD daemon gets quite irate and will eventually grill you piece by 
  piece on its trident