What approach should I have about foreground in a landscape photography?

Answer 1

It depends on what you are trying to do. You can focus on the foreground, choose a wide angle lens and use a small aperture to make sure the background is also in focus. Or you can focus on the foreground and blur the background. You can also blur the foreground and focus on the background. 

Answer 2

With few exceptions, most successful landscape photographs will have an interesting element in the foreground, middle ground and foreground.  This enables the photographer to create a composition that leads the viewer's eye through the image.