Think ahead - while sometimes wonderful sunrise and sunset shots can be taken spontaneously without any forethought it's often the case that the best ones come out of planning. Scope out places that might be good for sunsets in the day or two before your shoot. Look for interesting places where you might not only be able to see the sun track all the way down but there will be opportunities for shots that include foreground elements and silhouettes.
Find out when the sun will set or rise and get there at least half an hour before hand as it's often in the lead up to and the time after the sun appears or disappears that the real magic happens.
Shoot at a variety of focal lengths - wide angel can create sweeping landscape shots but if you want to sun itself to be a feature of the shot you'll want to be able to zoom right in.
Silhouettes as focal points, sunsets need a point of interest and one of the best ways to add one to a picture is to try to incorporate some sort of silhouette into the shot.
I take photos of the sunet, when ever I can. But between weather, where you are and what can stand as your focal point...it can be almost impossible. Try out for a day, check the weather, go to a place where you have a feeling that the photograph would capture beautifully and hopefully even catch a silhouette that could create the right amount of interest and color.