The Common Mistake
All too often I see people setting up the tripod as soon as they get to a location, before getting their composition! I encourage you to establish your composition with camera in hand without that cumbersome tripod dictating where you put your camera.
The Golden Rule
Always put your tripod to your camera. Never put your camera to your tripod. Get your composition first, then place your tripod to hold the camera in that exact position.
When you set up the tripod first, you're limiting yourself to compositions that happen to work from where the tripod landed. Instead, move freely with your camera, find the perfect angle, then bring the tripod to that spot.