HCI, design, and other similar programs should offer a one-credit course on how to build a portfolio. I'd love to teach it. Why? Because I see so many portfolios that are completely ass-backward.
Don't mistake me. A lot of the work is fantastic!
You should always start with the finished product and then work your way back, not the opposite, which is how most portfolios are. The core problem is that a lot of people aren't comfortable selling themselves. But that's what a portfolio is. It's a marketing and sales job.
As a quick aside: You will become a better designer, product manager, engineering leader, etc., if you spend some time learning sales and marketing. Spend one month trying to do inside sales with no leads on 100% commission.
A good portfolio and case study should follow one of two methods:
1. The inverted pyramid from journalism
2. Product marketing, similar to what Apple does on their website
Both methods focus on the most important information first and then work their way back. The big difference here is that the inverted pyramid approach would be more copy and more about telling a story. The product marketing approach would be more visual and might be broken up into discrete sections.
Regardless, both are the opposite of what I see in most portfolios.
Do you know how many times I have seen a portfolio piece or case study start with a photo of a wall of post-it notes? Did you also know that they also look the same? People are getting bored and leaving.
It's way too much process and not enough results. People who want to work with you want to see results. In the inverted pyramid approach, you will cover the who, the what, and the why.
Who worked on this project (who did you collaborate with)? What was the final result? Why is this a good product or feature? What did you contribute? What was the response from users?
In the product marketing approach, you are going to market this feature or product and your work on it to people. This is why it is great. This is why people love it. And anyone reading this should want to work with me.
Spend some time looking at the best product marketing websites in the world. Notice how Apple first gets you to want to buy the new iPhone and then explains how they built it and all the new tech that went into it?
Once you finish making people froth at the mouth with your work, then you can explain the process. Maybe you started with some How Might We's, then, made your way into affinity diagramming, then started crazy 8s, and then you busted out the voting dots.
Now if you are going to discuss your methods, they should be in service in selling yourself. You use these rigorous methods because they produce better, more consistent results that drive X, Y, and Z outcomes for users and the business.
It's a marketing and sales job and many of the people you are selling to don't even know the ins and outs of what a good process looks like. Focus on what they can understand.