Is not a easy job to create a successful showreel. Nowadays, there are to much competence outside in the market, and this is a really thought industry and therefore, is a hard job to create a proper showreel.
Here is an example of my old showreel:
I chose the follow showreel, because I think that is a great example that how a good camera/editor has to be in terms of TV/Corporate productions.
About the showrell itself, is a good example in terms of structure ( divided in parts/ different types of work), Music and Shots quality. Shots are really important with the showreel because they are your presentation to the potential employers. Always is better the quality instead of quantity.
Have a look: