The Common Mergansers (Mergus merganser) pictured above are posted just to give some idea of the weather yesterday - a nice bright day but VERY windy. Below I discuss what little I have learned about composition.
I think of composition as what is inside the frame and how it is organized. That seems a little vague but it addresses what I feel are the big problems I face when taking photographs. First, "what is inside the frame," is a consideration for me because I tend to want to get everything possible into every picture. You know, here's a picture of Jack standing beside the dinosaur and the two of them are standing in front of the parliament buildings over which the Blue Angels are flying in formation to celebrate the eclipse of the sun just visible to the left near the tornado.... There are probably six good pictures there but how often I end up trying to get them all in one frame still amazes me. However, I have learned a little bit about editing and the rule here for me is to decide what the picture is about and then (if possible) get rid of everything that doesn't lead the eye or mind to that subject. When taking photos that usually means zooming in or moving closer or narrowing the depth of field.
At home, cropping can often solve the problem of too much stuff in the picture. In the Fisgard lighthouse picture below cropping the bottom and the left side removed most of the distracting driftwood and the equally irrelevant Esquimalt Naval dockyard.Insofar as how the remaining information is organized inside the frame the two rules I generally go by are leading lines and the Rule of Thirds. There are lots of lines in the world - the horizon is one, but there are lots of fences, roads, pathways, shorelines, windrows and drifts, treelines and snowlines, etc. What I look for when framing a photo through the viewfinder is lines that will lead the viewers eye into the photo and towards the subject of the photo. In the lighthouse photo the two main lines are the shoreline that pulls the viewer's eye from the bottom left and the road that does the same from the right. Though they are less distinct, there are a couple of lines in the sky that also lead down towards the lighthouse. This is one of those things that you really have to concentrate on when taking a photo because if you don't get the lines in the right place there is not much you can do about it later when processing the photo. Of course there may not be any lines in the environment or they may be useless for your composition in which case you have to do without.
The Rule of Thirds has to do with where the subject of the photo is located. Space inside the frame is divided into thirds by two lines drawn across the frame and two lines from top to bottom making 9 boxes. The rule of thirds advises that the most pleasing or interesting compositions are when the subject of the photo is situated where two of these lines intersect. Most of us naturally put our subjects in the center of our photos when we point our cameras. I'm getting better at framing things when I take the photo now and managed to place the lighthouse in this photo almost exactly on the lower right intersection. I've also emphasized in green the leading lines in this photo that pull the eye towards the lighthouse.Another rule I often use for landscape photos is something I read somewhere: "foreground, middle ground, background." In other words, a landscape photo with something fairly close, something a little further away, and something far away makes a more interesting photo than one in which everything is very distant. If you're on the summit of a mountain, try to get a bit of the summit in your photo of the vast view. It gives the viewer a place to stand and puts everything into an understandable perspective.
There is a great deal more to composition. Above are just a few guidelines I understand and use regularly. Sometimes, as in the photo below, I am very pleased with how it all works.