When I first started at Pixar there was a wall of fame of demo reels. Back then, demo reels were on VHS tapes or even bigger D1 format tapes as big as a dictionary. The demo reel cases were decorated with all kinds of different packaging to attract the viewer.
I remember one that was a clay sculpture of a person reading a paper where the headline said, 'Animator gets job at Pixar'. The amount of trouble that the artists went through to be noticed was amazing. The problem was, the content of the reel was not enough to get them an interview.
Having been involved with the artist training at Pixar I have seen a lot of work come in and out, and I can say confidently there are many different types of reels. The reality is that if a demo reel does not capture the attention of the viewer quickly then it is very quickly changed out for the next one. I know this sounds harsh, but there are so many reels sent in, it's simply the reality of the situation.
01. Tailor to the audience
If you are a VFX animator but want to break into feature animation, showcase the work that displays your potential as a feature animator. If you are applying to games, then show how good you are at action, and so on.
02. Keep it simple
Place your name and information at the beginning and end of the reel. Choose music that does not upstage or drown out the animation on the reel.
03. Keep it short
There is no reason to put everything you have ever animated on the reel. Nobody cares about bouncing balls. Potential employers want to understand that you have ideas, character, acting, physicality, appeal and so forth.
04. What work is yours?
Animators should separate scenes by colour or title. You don't want to claim any work that isn't yours. It's a small industry, people know who did what. A reel breakdown is a good idea.
05. Start and end strong
You should hook your audience with great work and end on something special. I've been in reviews where someone would pop in a reel and fast-forward until they saw something good.
06. Make sure your reel plays
About a third of all reels we receive do not work. Make it fool proof. You can do this by providing a link to your reel on a website. Most people do not have physical reels anymore, but it's still nice to look at extra material.
07. Show personal work
If you are a professional who is not getting the chance to shine with the work you do day-to-day, then animate something you would want to do instead and include this in your reel. Some of the best reels I have seen have good work, done professionally, but had some amazing personal tests that showcased acting and performance.
08. Always be original
One thing that really bugs me on demo reels is when I see a stock rig on a grid background. I want to see what you bring to the test you are animating. Who is the character lifting the heavy object? Where are they? Why are they doing it? Give that assignment context. Show them you, not that boring grey colored rig you downloaded.