I like to put my photo editing into three categories. The first is photo "clean up" where you really aren't changing anything substantial in the photo, just making it more pleasing to the eye. Things like cranes, power lines, skin blemishes, etc are all fair game. The next category for me is photo "enhancements" where you have a picture that you alter in a major way to improve it for your personal use. For example, if you take a picture of your cub scout son holding the flag, but there is somebody behind him and you would like the picture of him by himself to send to his grandmother. Like this:
The last category for me is photo "manipulation". This is where you take a picture and instead of making it a better version of what it was, you change the nature of the photo all together. This can be fun, such as when you tell your sister that you were there at her baby shower in Idaho three years ago, when in fact you were back home in Seattle. With Photoshop you can make the facts be whatever you want them to be, like this:
For this picture, I took a picture of myself at home in front of a white wall and pasted myself into a picture of her babyshower. Its not a very good job and would never hold up in court, but for a second she had to think to herself "maybe he was there".
The first one my wife did and was her first try at editing. The second one I did a while ago before I got Photoshop, I just used the software that came with my camera. Anybody can do it, but some pictures and projects are easier than others.