Size and Scale
Familiar objects show off the scale of the landscape
This tip will make a big difference if the intent of your landscape photo is to show the size and scale of the scenery.
The hard part is determining what familiar object or subject you're going to include to show scale.
Lack of Scale
Many landscape photos are taken with no scale included. There are thousands of shots of the Grand Canyon where there is no reference point to determine the actual size of the canyon.
This actually makes sense: most landscape photographers want to focus on the beauty of the natural landscape. When the canyon is the subject of the photo, why include a bunch of extraneous reference points? It only detracts from the simplicity of the scenery.
If the goal of your photo is to capture the beauty of nature, then focus on that. However, if the focus of the photo is to show just how enormous the landscape is, you have to include something that provides a sense of scale.
Include Something Familiar
Here's the easiest way to provide a sense of scale: put a person in the photograph. We see people on a day-to-day basis, and we are all very familiar with just how tall a human is (even though humans vary in height). When you put a human in the natural landscape, it immediately shows the size and scale of the surroundings.
Here's an example: you take a photograph of a fallen tree in the woods. Since it is your intent to show the size of the tree, you place your friend next to it. When everyone who looks at your photo sees that the tree is twice as tall as your friend, they have an immediate reference point for the scale of the tree.
Don't feel that you are stuck using people all the time. Any familiar object you can find will help illustrate the size of your primary subject. If you photo is of a waterfall, include a tree. If you're snapping a river, include a boat. Airplanes, cars and buildings also give a sense of scale. All you have to do is pick objects that help your viewer perform an immediate comparison of size.
In the photo on the left there is no scale — it's hard to tell just how large these rock formations are. In the photo on the right, there is little doubt about how large the rocks in the background are. The person in the foreground helps illustrate the scale.