After taking 4,000 photos in seven months, here are the tricks I have learned for taking good digital photos.
Experiment -- There is no penalty for taking too many digital photos. If they do not appear the way you like, simply delete. Try different angles or different framings of your subject and choose the best. Play with the features you do not understand until you see what they do to the photos. On occasion I take my amber clip-on sunglasses and hold them over the lens when shooting into a bright scene. Everything looks better in amber anyway.
Sunlight -- Unless you are shooting black and white film, quite impossible with a digital camera, wait as long as you can for the sun shine on your subject (unless of course you wish a night scene). There is nothing you can do in Photoshop to make up for a lack of sunlight. With bright sun, the colors will be vibrant; without it they will be dull. This may mean returning to take a photo on another day.
Contrast -- The position of the light will affect the placement of the shadows. Shadows will give contrast, defining edges, and give depth to your subject. Often the best time is when the sun shines slightly across the subject. Consider the effect of sunlight in the morning or evening, e.g. the direction of the shadows or the color of the light (sunlight gets yellowish in autumn).
Fill-Flash -- When an object in the foreground is dimly lit, it will appear more like a silhouette against a brighter background. In this case it may make sense to force a "fill-flash" in the manual setting. Simply set your camera to manual and turn on the flash. This will illuminate the foreground so it can be seen better without affecting the background. Just beware of "flash burn," areas that are too bright as a result of the flash.
Depth -- A photo is effectively monocular and therefore does not have the depth perspective which we get from two eyes, thus it is important to add this information with other cues. An example of this would be my photo of the dunes in Merzouga, Morocco. The mysterious curves and subtle contrast of the dunes beg for photos, but without having the two people in the distance the audience has no clue how massive the dunes are. At the very least consider shooting something interesting in the both the foreground and the background.
Composition -- Look at postcards when you are in cities. Not only will you get a better understanding of what is photogenic, you will begin to learn what makes a good photo. Certain lines draw your vision into or out of the scene. There is no easy way to explain, just look at what good photographers do, and you will begin know.
Eye level -- When taking photos of people, generally shoot them at eye level and leave plenty of space above their head (even consider leaving out their feet). Usually the person should occupy about two thirds of the vertical space.
Photoshop -- Nothing beats the power of Photoshop. Other image manipulation software can do a fine job, but the control that Photoshop gives is awesome. Usually the auto-adjust works fairly well, though it can destroy the color balance, in which case try the auto-adjust of the brightness and contrast. If all else fails, do it yourself. Another useful tool is saturation, which can help bring out the colors. Like I said before, don't be afraid to experiment. However do be afraid of image compression--Photoshop will sometimes compress your photos beyond where they will look good on a high resolution printout. When in doubt, "Save as" the photo and control the level yourself. A sign of this is when the file size is much smaller than you expect them to be.
Crop -- In the digital world you are no longer constrained by the aspect ratio of normal photography. There is nothing which says your photos have to be 1200x1600. I often crop my photos so that the image has a nice composition, just be careful not to crop too close because the cut portion is lost once you save your changes. A bonus is that the files will be smaller with the useless data discarded.
Spot metering -- I said before to experiment, but this one is important enough to mention. Automatic cameras set their exposure automatically, averaging the amount of light of the entire scene, though giving importance to the center. The Canon PowerShot S10 allows for Spot Metering in the manual setting. Instead of averaging the whole scene, the chip now concentrates on the center. I often use this feature when shooting a sunset. Center the rectangle on the brightest element and depress the shutter halfway. This will lock the focus and metering, allowing you to frame your shot before depressing the shutter all the way.
White balance -- White balance is usually set to automatic. This means that the internal programming decides what kind of source is illuminating the scene. There are times when the camera gets this wrong. In manual, you can override this--for instance telling the camera to react as if the light were from electric bulbs (yellowish) or from fluorescent lights or a hazy day. The camera can now compensate properly for the light.
Night photos -- Little cameras have little flashes. If your subject is at some distance, do your battery a favor and switch off the flash. A night scene has very little light, so you should open the shutter longer. On my camera I set the "Gain" to "1.0" or "2.0", though now the shutter will be open longer, meaning the camera must be kept very steady (possible by hand on "1.0", not higher). In the last case, since I can't carry a tripod, I use the timer function. I set the camera on something firm, press the button to start the countdown, and wait for shutter to snap. Presto, instant tripod!
Vision -- Most important is to begin to learn to constantly imagine what you see as a photograph. If you practice, it will soon become second nature, and you will be thinking like a photographer.
Printing -- Shutterfly.com has the best printer for digital photos. You can upload your photos to their site, order prints, and they will arrive in the mail. This is not exactly cheap, so do it only for the ones you really want.