When you are shooting for print and especially a magazine you would compose some photos for the cover. You leave a little more space than you would had you not been trying to make room for the text that needs to be on the cover.
Most editorial photographers are paid more if the photo runs bigger as well as for how many photos they use in the printed piece. Getting a double-truck [two full pages--side by side] also will give you more money. Here you have to take into account the gutter, the place where the two pages are divided.
Sometimes they use one photo that bleeds off the pages or sometimes a grouping like here above. Most designers are aware of the gutter and minimize this affect on the image.
Knowing you are shooting a photo story most pros will do all they can to make the images so good that the editor feels like the story must be on the cover and get extra pages. This not only helps the story be told, but the photographer also benefits from a bigger pay check.
The designers used to joke with my mentor, Don Rutledge, they they thought he had templates inside the viewfinder to help him help them with layout. Really Don shot so many variables in situations that for any situation he usually had a cover shot, a double truck, some variation of the double-truck and then some tighter shots for impact.
Today the most likely place your photos will be seen are on the web. This is a horizontal space and the general rule of photography is to fill the frame of the camera and watch the corners. This also applies to your photo when filling the hole the designers are working with on the computer screen.
This is how a vertical shot will look in the space for a designer. This is the space it would fit within a video. The video format is about 16:9 proportion.
My suggestion is to shoot a little looser giving some room for the cropping. I know some photographers will even put some guides over the LCD screens to help them with their framing.
If you really want to grow your business, be the guy that not only shoots for the use that the project is intended, but to meet other uses. This is great stewardship because you can show to the client that they now can use your photos for many other things from brochures, newsletters, displays, PowerPoint, websites and more.
Besides understanding the proportions you need to think of what they audience is using to view your work. This is where knowing your demographics can help you plan the coverage better.
What it the photos are going to be used in a video that will be put on a website. Now if your audience is mainly going to the web through a desktop or even laptop you would shoot this differently than if they are using a Smartphone.
If the experience will be on a mobile device like an iPad or iPhone, then shoot tighter. A panoramic shot with a person in the corner just doesn't read well on a 3" screen. This is where tight shots of faces and objects are better for the space.
Think of how you tell time. Be sure the face of the clock fits the space to be able to tell the time.
This photo of the watch makes it easy to tell the time.
As you can see in this photo the watch and clock are about the same size. If your point is to see what time it is, get closer than this photo. On a iPhone in a video playing at full speed this image would loose it's ability to communicate.
Are you asking the client, "What is the end use of the photos?" If not you need to do this and then you need to plan to be sure your photos make the best use of the space.