Hmm... I can't think that I would ever alter the foreground I just tend to look around until I find something that I can use to try and add depth and lead the eye into the picture. If I can't find anything at all (which is quite rare, you just have to use your imagination sometimes and get a little creative) then I'll move on to another location.
Sometimes I'll swap the sky for something a little more dramatic but I don't do this often as it has to look 100% natural.

www.natural-photo.co.uk

"Dodging and burning are steps to take care of mistakes God made in establishing tonal relationships.  ~Ansel Adams"