My portfolio changed a thousand times through the years. I would not dare to show my first portfolio right now! The feedback of how people experienced it was crucial for my growth. I had included every sample of everything I ever did, from communication advice, websites I built, paintings, poetry and photography. I remember people telling me "But, what are you then?". I used to reply "It's a new age, we can be everything" The only problem was that people didn't know what to hire me for. Friends with companies said "I want to work with you but what do you do?"
It was hard to focus but I went through a selection of what I was better at and what I enjoyed doing the most. Right now I only do photography.
In a class of from Joey Lawrence I learnt to organise a portfolio by colour and so create smooth changes of mood. He showed his print portfolio and how he would make the pages match with eachother and I applied this to my online gallery. I started either by cold images (blue, green, purple) and slowly build up to yellow, like a climax of colours and then pass to red to conclude in a strong emotion. This details have generated a ton of compliments about my portfolio, without them exactly being aware why, it just feels good and it looks clean. I have no OCDs (not that I know) but imagining the website from a perspective of a heavy OCD person helps me to pay attention to detail.
Another thing that I learnt from working for 3voor12, a music news platform, is that you either includ colour or black and white images. You cannot mix 2 black and whites, one colour and one black and white again. You can place the b&w by the gray or black images or just leave them for the end.
3. Meticulous selection
Kill your darlings. We all ever had a clients with such a clear vision of what he/she needed that it does not represent your work but someone else's.
I would not include that in my portfolio at least I am proud of it. I do mention the company on my client list but I don't include the images on the gallery.
A great photographer looked at my portfolio a few years ago and asked "What do you want to be hired for? Take out everything that does not lead you to that sort of ideal projects!". The selection afterwards was natural, potential clients who did not like the mood in my portfolio simply did not work with me and I am glad I did not worked with them. I had time to work with those who enjoyed my work and I felt motivated to create something amazing, together with them.
Better include 5 works you feel that they truly represent you than 100 sort of just alright samples. You don't have to share everything you have done since your potential clients don't have the time to look at it. Just share the ones that will lead to a "Yes we want to work together".
4. Client cases.
A client once mentioned that they had chosen me because I had included some samples of work I did for other company similar to theirs. So they felt I had the experience in this and they could trust me.
Don't forget to add tags, titles, description and metadata to your images. All this helps you to build a history on Google which brings you every time higher and higher on the list. Sites like Wix have great SEO optimization tools. Also, instal Google analytics so you can measure your target group statistic (locations, language, age range, etc).