If you're shooting in anything outside of mid-day sun, a tripod is usually a good idea. The hallmark of a good landscape is a really sharp image. Here are some general tips:
1) Use a tripod. Period.
2) Use a remote shutter release.
3) Utilize your camera's mirror lock up feature. This will require you to press the shutter release twice to get the image, but vibration will be reduced from the mirror locking up on the first press of the release.
4) Turn off VR/IS if you're on a tripod.
5) Shoot at f/8 or f/11 for the best contrast/tones (general rule of thumb is two full stops from your len's aperture).
6) If you're in *really* bright sunlight, yeah, maybe consider a polarizer filter.
7) Try to shoot using a wide angle lens if you can -- landscapes are often about evoking a feeling of cascading fields, dunes or trees. I've found I can accomplish this better shooting at 10mm than 200mm.
The above are my opinions.
