Someone in my network wanted guidance in building a professional (often software-related) writing portfolio for the first time -- they want to give other people a portfolio of work they've already done, so that those people can consider hiring them for paid writing gigs. This person wanted advice on what to choose, how to curate and structure and present the portfolio, and whether to keep it private or publish it somewhere public.

Here's some free advice on getting started with that. I'm sure there are better ways to do this and be more polished in the final presentation, but here's how I suggested they get started.

1. Start by taking 1-2 hours to assemble a big rough list of what you've written, in the last 10 years or so, that you might conceivably want to share in this portfolio. Be wide and inclusive, and if this feels overwhelming, remember that this does not have to be comprehensive -- you just want samples of different categories (like "neighbor-friendly explanations of technical topics", "bug reports", "profiles of individual people", "replies to support requests", "nonfiction essays", "research papers", "public conference talks", "HOWTO tutorials", and so on).
2. Decide whether this will be a public or private portfolio. If most of these pieces are ones you really don't want to share, online, with the public, under your wallet name, then you're going to be doing this as a private portfolio. Otherwise you'll turn this into a page or subsite of your public website, and you can mention and summarize the private pieces and say "available upon request".
3. Select the best 1-3 examples for each category. This might involve digging because maybe now you'll remember another category or another piece.
4. If it's a private portfolio, turn the whole thing into a giant PDF with chapter headings explaining what category each item is in. If it's public, do that, but also make a webpage -- Heidi Waterhouse's list and Betsy Haibel's list are straightforward examples you could use as patterns. If you want to be a little more explanatory and give the reader more guidance about the context for each piece, you could do something like what Lindsey Kuper does. And if you want to get really intense about it you could make something like what I've done with the Changeset Consulting "resources" page, with stock art!
5. Every few months, review what you've written and see what you need to add to the portfolio. (I also keep a public mega-list of nonfiction and fiction, art, software, and zines I've made and a big list of my past talks, interviews, and stand-up comedy, which helps me when it's time to update the Resources page for Changeset.)

If you've been thinking of making a writing portfolio and putting it off, I hope this structure makes it more feasible.