Editing can turn a good photo into a great one. It is also an important part of the photography process that allows you to manipulate your photo so it looks exactly the way you want it to look. There is no right or wrong when it comes to editing your photos; it is just a matter of using the tools you have available in order to get your idea across.
Regardless of which editing tool you are using, chances are it has the following options to use to edit your photo:
Saturation refers to the vividness or boldness of the colors in your photo. Increase the saturation to get bolder, vivid colors. Decrease the saturation for muted and more subtle colors in your photo.
Color balance refers to the color temperature in your photo. A warm color balance setting will bring out warmer colors like red and yellow in your photo, while a cooler color balance setting will emphasize colder color tones like blue and green.
Contrast refers to pushing or pulling middle color tones in or out of your photo. When set to the extreme, a high contrast setting will polarize the whites and blacks in your photo, so the colors are either extremely black or extremely white. A low contrast setting will make the photo totally grey.
Brightness/Density often works hand in hand with the contrast setting by making a photo lighter or darker. You generally want to adjust brightness and contrast to correspond with one another.
Most editing tools have other options as well, like converting a photo to black and white or sepia, but start with the four features above to develop your photo editing skills.
Almost every professional photo you have seen has been edited in some form or another. The people who edit these photos are professionals, so the number one tip for editing is: do not get discouraged if your photos still do not look like professional photos after you have edited them! Spend some time playing around with your editing tool to get familiar with the effect of each editing option. Start by practicing the four items I listed above. A simple change can have a dramatic effect on your photo, so pay attention to cause and effect as well. Also, it helps to print out a small test shot before you order a large print or photo product, just to make sure the final print looks similar to how the photo is displayed on your computer monitor.
Keep at it; eventually, editing a photo on your computer will become as familiar as taking a picture with your camera!