How to touch up photos using Picasa
You can easily tweak and touch up your digital photos using photo editing software. Doing so can improve upon the original image, or allow you to add special effects that make your photos more artistic. Picasa is an excellent, versatile and easy to use software from Google that lets you touch up your photographs in various ways. And it's free!
Download Picasa from picasa.google.com, and install it.
Once you have set up Picasa to find your photos on your hard drive, select a photo and double-click on it. This will open up the photo for editing.
Look at the editing options on the pane to the left of the photo. There are three main tabs: Basic Options, Tuning, and Effects. In basic options, use Crop if necessary to keep just the portion of the picture that's of most interest. This might be useful if there is a focal object of interest in the photo that you want to emphasize. In this case, cropping helps remove the extraneous background elements, helping to emphasize the interesting part of the photo. You can also use Redeye to remove red-eye effect in flash photos.
Play with various options from the Tuning and Effects tabs to see how this affects your photo. Under Effects, sharpen and saturation might be two especially useful options. They sharpen the image and make the colors more vivid, respectively.
Save your photo once you're satisfied with the results.
Tips & Warnings
Always make a copy of your original photo, and use the copy to touch up in Picasa. That way, if you're not satisfied with the result, you still have the original.