The first two keys to a nice landscape photograph are pretty obvious. First (and foremost), photograph an interesting subject. Second, and slightly less obvious, is to photograph in good light. This usually means shooting at dawn and dusk. The third key is even less obvious. It is utterly missing from the following image of the Grand Staircase in southern Utah:
Let us move the tripod a bit and take another image:
Much better! Now the third key becomes evident: a strong foreground. Even better would be a strong foreground and strong middle ground. Imagine what this image of the Golden Gate Bridge (a larger image can be found in the Landscapes gallery) would look like without the chain in the foreground:
Without the foreground chain, I suspect it would look pretty ordinary. Ideally, the foreground (and middle ground) are both strong and lead your eye to the subject. This is evident in this image (a larger version is in the Landscapes gallery) of a small waterfall at Sunrift Gorge, Glacier National Park, Montana:
Here, the two logs lead your eye to the main subject: the waterfall. The logs are assisted by the fan-shaped flow of water beneath the fall, which also directs our eye to the subject. It took me awhile to learn about this third key. Hopefully, you can avoid the pitfalls of mundane landscape photography by always looking for the strong foreground.