Watch out for lens flare. Even if there isn't obvious glare, it's easy for sunlight to come from the side and cast flare across the front of a wide-angle lens. You can lose 50 percent of your contrast and color saturation in the scene -- when I first started shooting landscapes, I didn't even realize this was happening in some of my images! Always check the front of your lens to see if any light is hitting it. Use the lenshood, your hand, or a hat to block any sunlight from ruining your shot (but be sure not to let it wander into the frame -- another reason to use your tripod).