A lot of freelancers I've found try way to hard to make their portfolio look amazing by applying crazy styling and adding as much information as possible.
Of course, everyone always wants their portfolio to be better than everybody else's so they'll do whatever possible to make it better. By doing this I've found many freelancers become distracted and don't concentrate on how to best showcase their work, but instead showcase their portfolio.
One quote which I've always stood by which mainly applies to web designers -
Never trust a web designer whose website is better than their work.
When you're a freelancer you always need to be improving your skills and keeping up with current trends. That means your work should always be better than portfolio site.
How To Improve Your Portfolio
Make your work the front page
If you're a graphic designer, web designer or photographer, show off your work on the front page. Unless you're an agency, you don't need a front page showing off your company and what you do. Put your name in bold at the top, with a small sub-heading which is really simple like "web designer". Then add a lot of white space around your name and sub-heading. This will help people remember your name and what you do.
Use huge thumbnails/images
Anyone can be a potential client so having huge thumbnails on your front page can help your work get a lot more noticed than you think.
If your work is good it'll do the talking for you. You'll be proud to show it off and will be happy to show large thumbnails of it. Because people will get a sense of what it is, they will know if they're interested or not at looking at it.
Why Don't We Try's portfolio is a great example of a portfolio using large thumbnails. He knows his work is good so he doesn't need to make his portfolio look pretty because his work does that for him. His work is very bright and colourful and with large thumbnails you can tell what each item may be about. Such as the iPhone app with the screenshot within an iPhone, same with the iPad app.
Do you really need to make it responsive?
What market are you trying to target? Most likely it'll be clients who are going to be paying you £40 an hour and maybe have small to medium sized businesses. These people won't be using their phone or tablet to look for a freelancer. They will set time aside to look for a freelancer and the time spent looking for one will be on a proper computer. They want to see large images and a mobile or tablet will not be able to provide them with that.
It's understandable if you're a web designer to apply responsive design, it should be part of your skills. But a graphic designer or photographer won't need it too much.
Of course it's still a good idea to make it responsive but I wouldn't worry so much about it.
No one cares about your client's names unless they're big companies
Let's be honest, do we really care you did this project for John Doe? No not really.
No one actually cares about who your clients are unless they're big names like Nike, Samsung or Red Bull.
Pahhh, you can forget about that.
Make it minimal
When creating a portfolio site make it super minimal. It has huge benefits. Minimalism will not go out of date any time soon. It requires less maintenance. You won't need to update the design too often at all. And again, makes your work do the talking.
Claire Coullon has a great example of a minimal portfolio with colours to suit her work. She won't have to change much about it through the years and she has all the main information she needs right there on the front page.
Only show off your best work
I see countless photographers who just upload all their pictures to their portfolio. They think the more photos the better. That's a completely wrong way to go about it.
Only upload your best pieces, even if it is 10 out of 100. I would rather look at 10 absolutely amazing pictures than 100 average looking ones.
Edward McGowan is easily my favourite photographer at the moment. His pieces are amazing and he inspires me hugely when I take photos.
He probably takes hundreds of pictures every month but he'll only ever upload one or two pictures a month. Sometimes won't even upload a picture for two months. He only ever uploads his best pieces, pieces which he's proud to show off. People have now recognised him for his photography and he's become a popular member on Flickr.
Do not put your pricing on display!
This one I think is hugely unprofessional. When you're a freelancer you won't know the price for any project so how can you put prices on your website, every project will be different. You also won't be able to change your prices as you develop and become a more skilled freelancer because when you do clients will think you're charging too much.
Those are just a few ways to let your work do the talking for you. When you can achieve that clients will already assume you know what you're doing, you'll come across as a professional freelancer.