You get the best light at the following times:
- Sunrise: For about 30 minutes before sunrise, and for the 2 hours after sunrise you get the best morning light. The quality of light even drops-off between sunrise and 2 hours later. If you want great landscape photos get you buns out of bed early and go take some photos, you can sleep when the light is bad.
- For the 2 hours before sunset and during sunset you get the best late-day light. For sunset photos, you should also stick around for another hour after the sunset, sometimes this is when you get the best photo.
- During overcast days: this can create some very interested light and mood, the more heavily overcast the better.
You can have the best camera and lenses in the world, but if you go take outdoor photographs at 1 PM, good luck getting a really great photo. The majority of 'awesome' outdoor photography takes place during the conditions/times above.
If you want to make great photographs put yourself and your camera in front of a beautiful subject during these times - your odds of getting a great photograph will go up exponentially.