Depends on the role - front-end, back-end, full-stack, etc... that being said, the main thing I want to see is that you're passionate about your work. If you're applying for a full-stack position, you could have one project that you iterated on over 3/6/12 months, changed technologies, refactored, and ultimately built/released something. Also, as simple as it may sound, a meaningful commit message and git history is useful too. I don't want developers that `git commit -m "Updated stuff."`

Open source contributions to relatively established projects are always good too. That indicates that you've gone through a robust review process in most cases and have written some code that most likely had a good amount of eyes on it.

No general answer to that.

I look for a history of growth and accomplishments. I want someone who shows a focus on solving business problems rather than a focus on languages, tools, frameworks, etc. I don't care much about the kinds of projects, but if the portfolio looks like the usual university assignments or tutorial stuff (to-do list apps, for example) I probably won't care much about those.

Rather than worry too much about the portfolio -- which will mostly get barely glanced at -- research the potential employer, and ask questions about the business and organization. A candidate who asks "What project will I get to work on when I start?" or "What challenges does the business face this quarter?" will get my attention. A candidate who doesn't know what the company does, or asks about days off or which languages they can use will not.