http://www.youtube.com/watch?v=Qp-HMh-toHo
http://www.youtube.com/watch?v=HyXYCSGacUg
http://www.youtube.com/watch?v=El2QUTLLkIc

Most of the demo reels I viewed started off with the best foot forward, which makes a lot of sense. Start with the great stuff, and end with the good stuff. The stuff at the beginning grabs attention and ending good leaves a "good taste" in the mouth of the viewer. That doesn't mean you should bookend crap with quality, the entire thing should be of quality, but it makes sense to have your two best pieces at the beginning and the end. Most of the reels I watched contained an audio track but that may be for Youtube purposes rather than professional practice.