Think of dramatic vistas and the first lens that comes to mind is probably a wide-angle lens. There's nothing wrong with this as after all, they're great for getting huge amounts of the landscape in shot but next time you venture off into the hills, take your Tamron telephoto lens along too. Lenses such as the Tamron 18-200mm f/3.5-6.3 will give you a little more scope when it comes to framing your image. Don't forget your tripod either and a remote or cable release can be handy for minimising shake.
Find a spot high on a hillside that gives you a view of mountains/hills off in the distance as well as interesting foreground detail and you'll have the perfect set-up for your longer lens. Low light around dawn and dusk will work best for the shadowy silhouettes. If it's the shapes of the mountains you like don't shoot it with an empty, dull field in front of it. Instead, use the pulling power of the longer lens and bring the mountains to you, filling the frame as you do. This gives you the chance to photograph an over-done scene in a different way, bringing details not usually picked out with wide-angle lenses to you.
Leading lines such as fences and paths leading down the side of the mountain make good foreground interest particularly as they can be used to lead the eye through the frame to the detail that sits in the background. Look for large rocks, single trees, barns and other buildings that could give your foreground that little bit of interest it needs. If you don't mind waiting around until the sun sets these features look great silhouetted against the landscape that's still illuminated by the late evening sun.
If you have a misty morning, make the most of it using the perspective on your telephoto lens to photograph the distant hills which appear as stacked shapes. To emphasis this, make sure you're shooting in the direction of the light and watch your exposure as the bright sky can fool your camera. If this happens, try using a plus exposure to rectify the problem.