When photographing the sky during sunsets and during dawn it is very important to work quickly. The sun and lighting changes very quickly during this time and if you do not work fast enough, you may loose the perfect shot. Since the sun changes the sky so quickly during these hours, you can capture numerous different images from the same viewpoint.
When photographing during these hours, choose an area you know well. Shooting a place you know well is a bonus because you are more able to notice the patterns in the sky and the way the lighting changes. Use of a tripod can be very beneficial during this time.