Watch the Since You've Been Rockin' online guitar lesson by Angus Clark from Hard Rock Survival Guide: Rhythm
Follow that bass line! This will get you moving on your full chord shapes, and it's a great exercise for accuracy in the right hand. The second section is where you strictly match the bass as we negotiate some classically inspired changes. A little nod to "Since You've Been Gone" - Rainbow's first number one hit. The influence of classical music is second only to the blues in making the sound of hard rock, so if you don't have much experience with these kinds of parts or chord motions, this is a good place to start. This type of descending bass line is all over songs from Procol Harum through the Jackson 5 and all the way to Ozzy and beyond. Worth looking at twice.