Personally I love just grabbing my guitar... and noodling.
I'll pick a key, whatever strikes my interest at that moment, and start noodling just for enjoyment... and often times, I'll end up coming up with a cool progression or something that could be turned into a song.
This lesson will give a few of the nuts and bolts that can help you build a framework for creating progressions or songs on your own. You need to know what guitar chords work together, and you need to know what scale you're working with, and you need to have some idea of how those work so that you can use them to start getting creative. For instance, one of the most popular chord progressions of all time is simply a 1-5-6-4 progression. When you break things down into numbers like that, it becomes simple to build new progressions.
Video Problems? Watch it on YouTube