Perspective distortion occurs when you point the camera towards the subject at an upward angle. The effects are most evident with a wide angle lens and architectural details. You'll notice that buildings and towers appear to be leaning or falling over. To correct for this, start by moving further away from the structure. This will allow you to hold the camera parallel to the structure, greatly reducing the issue. If more adjustment is needed, you can then use the perspective tools in the digital darkroom to fine tune the perspective.
To make the most of these opportunities, try to center yourself to the subject. This will introduce a sense of symmetry and balance. Then, to make sure the whole frame is sharp, stop the aperture down to about f8. This provides the necessary depth of field while still allowing adequate light into the lens.
An often overlooked attribute of a tripod is that it forces you to slow down. By working more deliberately your exposure and composition will be more precise. It also opens up more creative possibility, allowing you to use extremely slow shutter speeds, or shoot in HDR.