Use the right equipment. There are a lot of good point-and-shoot cameras on the market now, and getting one that you do not have to worry about f-stops, focus and film speed makes it easier to concentrate on other things. You do lose some flexibility, though. With a camera you set you can do some fancy set-up, but for most of us it is more trouble than it is worth. And with digital cameras, the only kind you are likely to use unless you are a professional photographer, there are a lot less worries.
A built in, automatic flash is also very helpful. With it you get a flash when it is dark enough so you don't have to worry about your pictures being too dark. You can also use it to fill in shadows by covering the light intake and making it flash. This works well when you are in bright sun, to eliminate shadows from caps and other sources.
Set up your picture. Think about what you want in the picture. Do you want a lot of background scenery, or is the fish or person most important? Do you want to see the bait the fish was caught on, the tackle used, the boat or dock? Set up is critical. A single lens reflex camera shows you exactly what the picture will look like, so they are best for set up. Turn on your digital camera so you are looking at the screen rather than the viewfinder for a more accurate picture.
If you want lots of background, have the person holding the fish off to one side, not centered. Keep your frame low - lots of sky really does not show anything. A camera with a zoom really helps set up these pictures. The automatic focus should take care of that problem.
If the fish is what you want to concentrate on, have the fisherman hold it up near their face, a little toward the camera. Try to turn the back slightly toward the camera, too. The light belly on fish does not look as good as the darker back. And it is important to keep the eye of the fish in the frame and not covered up. Fish look strange if you can't see the eye.
Ask the fisherman to take off their cap, if possible. Caps throw a dark shadow on the face - that is what they are supposed to do - but that can mess up a picture. Also have them take off sunglasses or regular glasses. That helps get a better picture of their face. Try to get them to smile!
Get in the shade if possible to take your picture. Harsh sunlight makes the fisherman squint, the shadows cause problems and the bright light washes out colors. Get under a bridge, in the shadow of a tree or wait until late in the day if possible.
Study magazines and think about how those pictures you like are set up. Then try to see that same set-up through your camera when you are taking pictures to get the look you want.
Outdoor pictures are great for bringing back memories. Think about setting them up, use the right equipment and they are even better.