The most important thing to put on your demo reel: your name and how to contact you. Put at least those two pieces of information on your demo reel. Do it now. (If I watch a "demo reel" and it lacks these 2 things, then I just consider it eye candy from someone who doesn't want a job or recognition).
Also, add credits/make explicit what work is yours. Creating topical reels or reels categorized by your specialty makes sense. Another approach is using excerpts of your work with appropriate titles that point out your involvement in what we're looking at. You're selling us on what you've done; don't oversell by claiming expertise you don't have.
Online reels (YouTube, Vimeo, etc) are great, but also keep current version on thumb drives / DVDs to give away; some potential clients/employers are blocked from watching media sites at work.