Select Your Lenses
One of the best reasons to get a digital SLR is to take advantage of the opportunity to change lenses. One photo may benefit from a wide-angle view, while another shot demands a telephoto lens. But lenses are a significant investment--in some instances a bigger one than the camera body itself.
A versatile collection of lenses might include a wide-angle zoom to cover the range from 12mm to 24mm, a general-purpose zoom that goes from 24mm to 120mm, and a telephoto zoom in the range of 100mm to 300mm. Throw in a 100mm macro lens, and you've covered all your bases. It's important to keep in mind the kind of photos you typically take, however. For example, if you enjoy taking landscape and people photos, you may never need a telephoto lens. Some photographers are perfectly happy with a single, general-purpose zoom like an 18mm-to-200mm lens.
In addition to considering focal length, pay attention to the "speed," or f-number, of your lens. Fast lenses have bigger apertures (smaller f-numbers) and can shoot sharper photos in low light than their cheaper siblings can. For more information on lenses, check out "Demystifying Lenses