Carey aka Binky from mograph.net made a brilliant, four part tutorial on building a showreel. He covers all aspects from reviewing the available footage, designing an intro, selecting and editing audio tracks to the final edit – and he did it using footage from my own (pretty outdated and much too long) showreel.
The result is pretty interesting and almost makes me wanna hire myself :)
(though some of the shots Carey used where animated by my fellow colleagues Marko Pfann and Peter Pedall)
Edit: just noticed that parts two & four are blocked in Germany because of legal issues. Firefox with the Proxtube add-on installed might solve this problem.
Looking at the original reel
Selecting and editing the audio
Building an intro and starting the edit