Watch the Between the Chords online guitar lesson by Angus Clark from Focus On: British Metal
The rhythm guitar arrangements for a vast number of songs involve the combination of chords with riffs that connect them. By seeing the material in this way you can get a grasp of what the chord progression is separate from all the riffage. This will allow you to simplify the material in your head. It's also a great way to understand how the material is written. Iron Maiden and Dragonforce are both bands that use this technique.