Cloud photography is simple since the shapes and textures of their structures add to the beauty of the picture. But it requires careful metering of light and setting of aperture size. With a digital camera one can see the result immediately on the LCD screen to get an indication of the correct exposure.
You don't always have to include a horizon or structure as a foreground. But, where ever it is possible, try to include it.
Clouds are best photographed when they are distant, because the cloud bases appear mostly uniform white or grey, while the top and sides show convective structure.
Mostly, the cloud pictures are taken the standard way, with some horizon low at the bottom of the frame and the clouds showing over this. But one must also try other types of composition as well.
A beginner must try his or her hand on taking two types of cloud picture. First, take photographs by zooming in to a small area of a convective cloud like cumulus congestus, to show the convective cells. Secondly, photograph an altocumulus clouds with trees or houses silhouetted in the foreground.
For composition, one can have manmade structures in the photo along with clouds, but use them creatively or avoid them altogether. One needs to get creative while photographing common clouds.