As someone who hires people, the best folio is one that fits the job description I’m looking for Meaning you want to have some main focus in your folio. Are you a generalist? guy suitable for support? guy suitable for larger dev tasks? are you a technical/animator or rigger? are you somebody who lives and breathes engine skills (UE4, UE3, Unity)?
Make whatever you want to be or become your focus of your folio, and then pick support skills to show off. E.g. Scripting is always good. But art skills are important too (tech-ARTIST!). Why? I want to see how your observation skills are if you’re going to work with shaders, lights, etc. I want to see if you can make some decent UIs and think about usability if you’re into tools. If you’re into developing software, I care about readability, re-usability, modularity and documentations, because other people may have to work/maintain/adapt your software.
Things I don’t really want to see: MEL only scripting folios. Sure, you gotta know some MEL. That’s not the problem. Not showing me Python is the problem. Same thing for MXS only folios - you gotta throw some other skills into the mix (C#, or animation, rigging, etc).
Personally I hate demo-reels unless you’re showing something off that requires the format: such as a rig, animations, FX. Don’t show me code or you fussing around with your mouse pointer over a gazillion of buttons of your tool. Write a short paragraph introducing your tool, as you would on e.g. scriptspot, make some meaningful screenshots or even short animated gifs that load in every browser.
If you’re a senior TA you can go up to 1 page per tool, but keep an intro paragraph! When I look for people with specialist skills I appreciate it when I can dig deeper - if I want to.
I’m usually not really checking out tools or code myself, unless you make it super easy to set up. But I do browse docs and API documentation, if available. For pipeline tools, consider using diagrams explaining the pipeline and how your tool fits in.
If you have documentation, teaching, mentoring experience and have anything to show, do it! e.g. tutorials. (Eric Chadwick has a good section on this on his folio!)
Finally, I agree that curiosity, attitude, experimentation and open mindedness are most important, but I usually prefer to assess this in an interview.