Shoot RAW to Save the Complete Picture
Your camera processes images a few times in order to spit out JPEGs, compressing and converting the native data that it captures. Even if you set it to record a JPEG at the highest size and in the highest quality, you'll still lose details compared to the camera hardware's inherent ability. RAW pictures--most common on DSLRs--save files in the native format of each specific camera's image sensor. This means that the photos are less compatible with software in general, since the RAW format varies. But the trade-off is that you can process popular camera file formats on a PC, instead of relying on the camera to set white balance and other variables permanently when saving to a JPEG.
On your camera, enter Alt mode by pushing Direct Print or Shortcut. Push the Menu button. Navigate to 'RAW Parameters', activate Save RAW, and you'll see a dot confirming the choice. Push the Menu button again, and exit Alt mode using the same button that you used to enter it. Now a RAW counter should float over your camera's regular remaining-photos countdown, helping you keep track of space for these bigger files. On most cameras, you can toggle RAW mode by holding the shutter halfway, and pressing the joystick to the right.
Apple's Aperture, Adobe's Lightroom, and other photo software can natively read the files from most cameras that have RAW saving built-in. At press time, however, these wouldn't read the unconventional RAW images that we shot using CHDK; you'll need to use a different tool.
I like making simple edits on a PC or Mac with PhotoLine, which natively recognized the files in my tests. Alternatively, you can use other software to alter these true RAW files minimally into DNG images that retain RAW data while becoming compatible with standard image editors. DNG4PS-2, RawTherepee, and UFRaw are good options.
Add a Live Histogram
Your camera likely lets you review a histogram after you take photos, showing the graphed curves that represent color and exposure. If the curve is squished to the left and leaves empty space on the right, for example, your photo is probably too dark and underexposed. If the curve shows values across the entire graph, your image has captured a dynamic range, maximizing the possible highs and lows.
Those details are great for reviewing shots or editing in Photoshop, but they can be even more helpful as live feedback when you are composing photos. Many high-end cameras show live histogram details, but your point-and-shoot probably doesn't. The CHDK software can add that feature.
With CHDK running, enter Alt mode, and push your camera's Menu button. Navigate to Histogram Parameters, and change it to Show Live Histogram [Always]. Push Menu again, and exit Alt mode. Most cameras let you instantly toggle the live histogram by holding the shutter halfway down and pushing the joystick down.
Now you can track exposure and details while composing a shot. Especially in manual modes, you'll typically want to make the curve spread across the entire graph for perfect exposure. Note that in some situations, such as at night, the curve will still favor one side the the graph.