Taking silhouette shots can be as easy as pointing your camera at a subject and simply pressing the shutter button, or as intricately challenging as any other form of photography.
How equipped are you? You definitely don't need a special kind of camera to take silhouettes successfully, but as is usually recommended, the trusty old tripod is fairly essential, or at least have something suitable enough to stabilize your camera against induced blur or camera shake.
A lens hood would certainly help to eliminate lens flare, because more often than not, silhouette images will be taken towards the light.
A graduated grey, or neutral density (ND) filter will help to cut down on some of the background glare. As they do drop the light ratio.
You may want to use some form of flash (not too much or you could spoil the effect), to lighten some foreground elements, because shooting into the light will not only darken your subject, but also the foreground can suffer.
Lens type is not critical, but if you used something in the 28 - 200 mm zoom range, you would just about cover all requirements.
Film? Somewhere in the 100 - 200 ISO range. Such as Kodak HD2, but even Kodak 400 max will give good results. You digital players will have to sort that one out for yourselves. Black and white film will surely give you strong, silhouetted, monochrome images and even sometimes shots taken with colour film towards the light will end up with a somewhat monochromatic look, but a little bit of colour does add interest to these sorts of images.
When we think of the word "silhouette", we see in our minds jet black figures, or shapes, on a very palish, or white background. However, it is aesthetically more pleasing on a photography judge's eye if there is a certain amount of detail in the subject matter itself. Hence, that little bit of fill-in flash, as suggested earlier. How much flash to use, if any, will be dependent on the amount and direction of the background light source. Try not to have too much of the image blacked or whited out. These areas on a photograph are known as "negative space" and are unproductive in an image and are certainly frowned upon by judges.
What are the best suited subjects for silhouettes? I think anything that carries a strong visual element, or is mood invoking, but something that the viewer can immediately relate to. such as, the human form, animals like dogs or horses, for example. Trees, such as palm trees, or Pandanas trees, can create good moody scenes. Jumping Motocross riders can bring about dynamic action shots. And don't forget to make the decision as to which way you should hold the camera to take your shots, portrait (vertical) or landscape (horizontal) mode. If unsure, try a few shots either way and make the decision when you see the results. I suppose that's a digital advantage.
Lastly, try to have your silhouette subject/s stand out alone from other elements in the scene, or if there are two main subjects, it is best to keep them apart so that each subject is a separate entity and stands out from the other.
See also "Backlight Photography"