Watch the Iommi Swings online guitar lesson by Angus Clark from Focus On: British Metal
Section one is all about finding the right voicing and making sure it rings true so that you are creating the right space.
Section two is more challenging section, just a bit brighter than double time. Keep it clean but more importantly make sure it swings! The combination of muted picking, open picking, hammers and pulls are all essential to getting the feel right on this.
Section three is a chord figure still in triplet time. Here again, muting and accuracy with the pick are essential to keeping the part swinging.
The solo is straight up blues licks - don't skip this stuff - its all in the feel!!!