Of the three elements of good product photography, Composition, Light, and Exposure, Lighting is probably the most important. Good quality light gives you true colors, and presents the stage for proper exposure. But what is "Good Light"? That depends on how you plan to present your product.
Natural light is simply the light from the Sun. It produces the truest color and typically gives an overall more pleasing image…as long as you control it. For most sales situations, balanced, diffused lighting is the way to go. You know your lighting is balanced when shadows are soft and no portion of the product looks brighter or darker than the rest. Direct bright light, light sources too close to the subject, and direct flash will cause harsh shadows and bright reflections which distract from your product, as you can see in these images.
Soft to no shadows with even lighting across the image is the goal for this type of product photography.
Most non-professional photographers will tell you that the best lighting conditions are outdoors on a cloudy day. This is almost true. When using the Sun as your light source, overcast skies form a natural diffuser. The clouds scatter the light rays, thus limiting the amount of light that reaches the subject of the picture and balancing the light across the entire scene. However, clouds move. Just because you have set your camera for a perfect exposure (or your camera has set itself perfectly) doesn't mean that those settings will be correct one second later when you snap the shot. If a thinner or thicker area of clouds moves between the Sun and your subject as you release the shutter, your perfect exposure just went over or under exposed.
When shooting in natural light, it is best to find a shady area, like a porch, to minimize the undesired effects of direct sunlight. The shade of a tree can be tricky, as the direct sunlight will show between the branches, as you can see in these images. If you don't have a shady area, you can purchase a set of inexpensive sheers, hang them from a tree or other object, and create a soft box to diffuse the light on your subject. Changes in light levels due to clouds can never be overcome, so it's best to set up your shot, wait until the light stays even for a few seconds and take the shot. You can always tweak the shot in Photoshop or, if you are using a smart phone to take the picture, inside the camera edit features of your camera app.
Direct sunlight coming through a tree.
Same area as above only a few minutes later when a cloud passed by.
A porch provides the best combination of light and shade when using natural light.