The term 'product' can cover many different subjects, so condensing into a few words the principles of product photography is quite a challenge.
If you want your product to sell, it must look good or appeal to potential customers. Good images are often the first impression that is made, especially with advertising and promotion. If you keep a couple of basic principles in mind and develop your photographic technique, you will be pleasantly surprised at the results.
Same as for food photography - camera. tripod, reflector and external flash (optional). It is interesting to note that no flash was used in the examples on the right.
Principle 1: THE BULL'S-EYE
Anyone who has used a rifle or a bow will know that when they are about to fire, the bull's-eye is the only thing that matters. Nothing else exists except that small circle which fills the whole vision.
When you shoot with a camera, apply the same principle. Every image should have its own bull's-eye. It is the reason for the photograph.
Decide on what you actually want to capture and make sure that it occupies at least 80% of the viewfinder. Remember, the image is created in your head before you ever push the shutter. Visualisation before the event puts you on the right path.
One of the most common mistakes people make is to attempt to crowd too much into the image. Practice simple and tight shots. Fill the screen. This is especially the case for web images which lose quality and size when formatted. Ideally, taking a photograph using this principle should result in virtually no need for cropping. Shoot the final image from the beginning and maximise file quality.
PRINCIPLE 2: work your subject
A great advantage of digital photography is the luxury of being able to take as many shots as you like without worrying about the accumulating cost of film. Make the most of it and take a wide range of different images. Here are a number of ideas
vary your angle - high, low, left, right etc.
move in close with macro or wide-angle
move back and zoom in
shoot from above
move the reflector to different positions
This principle applies to all areas of photography. If something is worth photographing, then work the subject
Avoid shooting under fluoro or tungsten light if you can possibly help it.
Use more than one image if you need to. This web page is a good example of many images being compacted into a small space without sacrificing the integrity of the image. Clicking on a thumbnail allows viewing of an enlargment whie remaining in the same space.
Think carefully about the background. Keep it simple and appropriate. If in doubt, use a white card for a neutral background. These can be bought from an art supply shot for about $5.
If you are shooting packaged food beware of reflection from cellophane and plastic. Open the packet and photograph the contents with the packaging behind. One of the best ways to avoid reflections is to move in close to the subject.
One of the most common mistakes people make is to attempt to crowd too much into the image. Practice simple and tight images.
Practice makes perfect. Observe how others have successfully taken great shots and emulate them. Study their tehcnique and work out what they have done to achieve their results. Then, create your own image in your head and have a go. Each of these sample images were taken on the run and shot within a couple of minutes. You don't need studios and expensive equipment to produce good images.