Try to plan your photos before you take them as much as possible. Let your "artistic eye" do your initial editing. No amount of fixing in an image editor can salvage a really poor picture. However, many improvements can be made using image editing software.
Photo imaging software allows you to view and creatively manipulate your photos. You can crop, rotate, sharpen, soften, lighten, darken, change the color value, and apply various filters for special effects (among many other things).
Many digital cameras come packaged with imaging software, and your computers may come bundled with an image editing program. The programs vary in features, ease of use and cost. Some software companies allow a free trial period and permit you to download their product.
There are many others!! Check out Tucows.
Tips and "how-to's":
Plan a good composition before you take the photo. That will save you time editing it later on. Fussing around editing photos can be very time consuming.
Quick-Tips - basic directions for scanning and acquiring digital images to use for web, PowerPoint, MSWord, etc.
Keep File Size Small
Adapting digital images for different purposes
Refer to the tutorials in your image editing program.
Save as jpeg or gif . Reduce to 256 colors to save file size. For email try to keep the file size of image attachments to 100k or less.
320 pixels x 240 pixels or 3in x 4in is a good size for web and most basic presentations.
Remember when you change images, do a "save as" to give them a file name that is different than the original file name.
Try to edit your photos before you insert them in documents.
More editing "how-to's": Photoshop, PaintShop Pro, Corel, Xara, and Painter Tutorials