Related to the concept of foreground, mid-ground and background is the idea of leading lines. The landscape is full of lines, such as roads, rivers, hedgerows, shorelines and even animal tracks, and we can use these in our landscape compositions. The viewer's eye will naturally tend to follow such lines so they serve to lead the eye into and through the image in a very natural way.
While straight lines work well for this, for some reason I don't understand the human visual cortex appears to find broad S-shapes very appealing. It's probably got something to do with the appearance of certain parts of a naked human body, but I'm sure I wouldn't know about such things.
Leading lines can be obvious or subtle. Anything that allows the eye to follow a path into the scene will work, so be on the lookout for paths, streams and walls that will serve in this capacity. Use the lines to emphasise the main theme of the picture by making it part of the visual path.