I'm going through the process now of selecting images from the past year to update my portfolio with and it is not fun!
One of the toughest things to do as a photographer is to select your own portfolio. It is also one of the greatest skills you can have to market and promote your work. The impression that you give can make people want to see more or move on to the next web site, book or marketing piece.
For me it is one of the most stressful things I do, because I know it can make or break me. I've seen many good photographers select bad images for their portfolio. I've also seen the opposite where an overall weak photographer has a portfolio that is put together well and draws people in.
The first step is to decide what is worthy of making it.
It should not have to be said that the photos should all be strong technically, but unfortunately I see a lot of photographer's work where this seemed to be ignored. I don't care if you shoot architecture, fashion or product. Your photos should always be technically "tight" for your area of photography.
You want photos that show off your skill, but also photos that the viewer reacts to. The biggest challenge is to separate yourself from your work. Sometimes you have a subject that you really connected with, or you put a lot of technical expertise into a shot or you just have great memories about that day and location. We all tend to pick these pictures to show off, but they aren't always the best. Sometimes that person you loved working with, just doesn't capture the viewer's imagination or that highly technical shot did the job for your client, but wasn't a very exciting subject. Separating yourself is key. If you are able to do that, which most photographers have a hard time doing, then you have taken a huge step in picking the best photos.
Select the types of images you react to when looking at other people's work. Take the time to go through other photographer's website and see what you like and don't like. It will help a lot in narrowing down your own work.

A job that was a lot of fun to shoot for a big client that loved the photo, but is it really portfolio worthy? Probably not.
The next step is to look at getting rid of some pictures. As you become more experienced and you have more imagery in your portfolio, it is naturally going to grow a little. This should not be an excuse to keep those photos that just aren't as strong or are outdated stylistically. It is tough to know which ones to keep in the portfolio and what is getting outdated, but you must do it. Ask yourself...which pieces don't feel like my current work, either in quality or style. If you have any hesitation about it not making the cut, it usually shouldn't. This doesn't mean just because it is old that you should get rid of it. One of my best photos in my portfolio is one I took over six years ago, but it still gets a reaction from everyone that sees it.

An image of a man on a bus in Kathmandu that will be in my portfolio for years to come.
The final step in showing off your portfolio is to decide in what order to present the images. This can be as important as the photos that are selected and shouldn't be overlooked. The biggest key is that you want your portfolio to flow. It should tell the story of your work. Put images together that don't contrast in such a way that it is shocking to the viewer. If the person going through likes what they see, but then they click on an image that may be just as good but contrasts too sharply with the previous image, they will many times move on to the next photographer. Gradually flow from one look to another.
The other key in the order is to make sure you don't "load" the front of your portfolio. Many photographers put all their best work first and then as you get further down in the portfolio the quality goes down. This isn't lost on the viewer, whether they are an art director or a bride. Your weaker photos should be surrounded by stronger photos to help support them. And lastly you always want your last impression to be a strong one.

Is this really the last impression you want a potential client to have? (Actual final image from a portfolio. Photographer to remain unnamed.)
Lastly, get other people's opinions and listen to them! Get anybody you can, whether it is a friend, family, other photographers or someone in the industry. I have had photos that I loved that others shot down and even though it was painful, I listened and had a stronger portfolio because of it.
Which of these two photos is best? They are too similar to both make the cut. I used friends to help me decide (we went with the second one).


Now it is time to go to work on my portfolio! I just need a photo rep to help! :-)