White balance: fine tune colors with this adjustment--great for fixing orange or reddish skin tones you get at dawn and dusk.
Use the temperature and tint sliders to adjust the image until you get a more natural look.
In iPhoto the temperature and the tint sliders (and other tools) appear when you click on the Adjust icon.
Recovering highlights: if one part of your image is overexposed (such as the lightest areas on the tree root, above) the recovery tool may help.
Use the recovery slider to bring the bright spots into balance with the rest of the shot.
In Lightroom, the recovery slider is in with other Basic tools in the Develop module.
Saturation: use this tool to make colors pop (or alternately, to desaturate tones for a muted look).
But don't go overboard--Clark sticks to a maximum of +15. Many printers can't reproduce oversaturated hues.
In Lightroom, the saturation sliders are farther down in the Develop module. You can adjust the saturation levels of individual colors.
Contrast: make dark tones darker and light tones lighter with this tool. This adjustment helps subjects pop on photos with lots of gray and brings out details on distant peaks--but again, don't overdo it.
Adjust the contrast slider, as well as the brightness slider, to get the best results.
In Photoshop Elements, this adjustment box will appear when you go to the Enhance menu, and then down to Adjust Lighting.
Localized adjustments: this tool lets you fine-tune exposure or saturation on a small section of a photo, rather than changing the entire image.
For example, in this photo, we've lightened the hiker without lightening the sky. "This can take you from zero to hero pretty fast," says Clark.
In Lightroom, clicking the paintbrush will open the localized adjustments tool. A dot will appear where you begin painting the lightening (or darkening) effect. Hover your mouse over that dot to see what areas you've applied a change to.
Crop: remove clutter or dead space with this tool. Ideally, you do that when you compose the shot, since you lose data when you shave off parts of the photo in processing.
But when you need to clean up a hasty shot, cropping works wonders.
In Picassa, cropping is located under Basic Fixes. You can set your ratio and then click and drag across the photo to choose what will be included in the final photo.
Remove unwanted objects: use Clone Stamp or Healing Brush to get rid of small distractions like an inconvenient fence post or an unknown hiker.
These tools take sections from other areas of the photo and superimpose them over the objects you wish to erase.
In Photoshop, when you're using the clone tool, hold alt or option and click to "pick up" the area you want to use to cover over the distraction. Adjust brush size and feathering amount and practice using this tool to make it look natural.