Cumuliform clouds are best photographed from their side (at a distance), to show the convective structure better.

Photographing common clouds

There are no special techniques required to take good cloud pictures. Depending on the type of cloud, you will need either wide-angle lenses or more telephoto lenses. I recommend using a zoomlens or two, since it makes composition much easier.

Cumuliform clouds are best photographed when they are distant, because their cloud bases appear mostly uniform white or grey, while the top and sides show convective structure. If you photograph them somewhat distant, you will see more of the top and sides than when they are overhead.

Conversely, clouds such as altocumulus and cirriform clouds (cirrus, cirrostratus and cirrocumulus) are usually better photographed overhead, because these show structure better when you look up (since they are more or less stratified).

Stratified clouds, such as this altocumulus undulatus, show most detail when photographed overhead. If you photograph with the sun to the side, you can increase contrast with the blue sky using a polarizing filter.

Exposure

Clouds can be difficult to meter on. Therefore it is easier to use a digital camera rather than film cameras to photograph clouds, since often the photo may be underexposed (if you meter on a bright cloud) or overexposed (if you meter on the darker sky). With a digital camera you can see the result immediately, and while the LCD screen of a digital camera can't be trusted much, it will give you some indication of the correct exposure.

If you use film, meter on a part of the sky or cloud that looks medium grey, not white or dark.

Using polarizers

The sky around clouds is polarized to some degree, most around 90 degrees away from the sun, and least near the sun or opposite the sun. If you use a polarizer, you want to block out the polarized light from the blue sky partially, to increase contrast.

You must be careful doing this, however, since clouds are already much brighter than the blue sky, unless it is very hazy or dusty. It is easy to overexpose the cloud or underexpose the sky using a polarizer. Both will make your photo look very ugly.

Try a close-up of congestus clouds to show convection well. You don't always have to include a horizon or structure as a foreground.

Composition

I recommend you to not only take cloud pictures the standard way, with some horizon low at the bottom of the frame and the clouds showing over this. Try other types of composition as well. For instance, zoom in to a small area of a convective cloud like cumulus congestus, to show the convective cells. Or photograph an altocumulus field with a tree silhouetted in the foreground. Use your imagination and avoid things as chimneys, cranes, powerlines and such that so many people have in their photos. You can have manmade structures in your photo, but use them creatively or avoid them altogether. Be also creative and not only documentary!