I’ve even been known to use those “amateur” features – Digital Vari-Programs in Nikonspeak – the icons for portraiture, sports action, etc. All of these modes are just tools in your box; use the one that fits the situation.
Program (P). This is the camera’s basic exposure solution. It’s a pretty straightforward tradeoff between aperture and shutter speed, as shown in the D300 manual by the diagram on page 404. In sports photography, I often use this mode for crowd shots in bright light. I’m usually shooting wide angle, and this mode will give me both a reasonably high shutter speed and small aperture – enough to stop movement in the crowd and give a fairly broad depth of field.
Shutter Priority (S). This is a setting where you control the shutter speed, and the camera adjusts the aperture automatically to achieve proper exposure. I will often use this mode when using telephoto lenses in a stage or auditorium setting, where lighting may not be great and I want the greatest possible depth of field. I set a shutter speed that is fast enough to prevent blur (using the old reciprocal of the focal length rule of thumb, and proper handling technique) – for example, I’ll set a value of “200″ (1/200 shutter speed) for the 80-200/f2.8 AF-S.
Aperture Priority (A). This is probably the mode I used most often until the D300 came along and I switched to manual exposure mode. For sports, setting the lowest f-number (widest aperture) guarantees you the fastest possible shutter speed for freezing the action, as well as shallow depth of field to blur distracting backgrounds. Often times, I will stop down one below the widest aperture (say, f4 when using an f2.8 lens) as many lenses are not particularly sharp wide open. For non-sports shooting, controlling the aperture is primarily for controlling depth of field, allowing me to choose a narrow range of focus when I want to isolate a subject. Conversely, setting a large f-number (narrow aperture) maximizes my depth of field.
Manual (M). This used to be strictly the domain of control freaks, and was seldom a mode I ever used until the advent of Nikon’s ISO Auto Sensitivity Control and the Secret D300 High-Speed Auto ISO Trick. Turn off ISO Auto Sensitivity Control if you want absolute manual control, otherwise you can choose exactly the shutter speed/aperture combination you want, and let the camera adjust the ISO automatically to match.