Apple's iPhoto is a photo-management program that comes with every Apple desktop and laptop. It keeps your photos organized and has some basic photo-retouching commands that will help you out of a lot of problems.
It's not an industrial-strength photo-retouching program like Adobe Photoshop, but it is free and much easier to use. If you are looking for a more powerful, free photo editor, click here.
Of course, iPhoto works better if you get a few things right from the very beginning.
For the purposes of this tip, I'll assume you know how to get your photos on to your computer, and perform other basic Mac tasks.
1. Start at the very beginning
When you first fire up iPhoto, you'll notice a few categories over at the top left-hand side. The ones to worry about are "Photos" and "Events."
The "Photos" button will show you all the photos you have in your collection, ordered by the date attached to the photo file.
The "Events" button does the same thing, but it also automatically sorts the photos by time, and does a pretty good job dividing them into separate photo sessions.
For example, if you go on a hike in the a.m. and grab some nature shots, and then go out to a birthday dinner that night with friends and take some more, iPhoto will split the photos into two separate "events."