Watch the Stinking badges online guitar lesson by Jeff Scheetz from 50 Blues Rock Rhythms You MUST Know
Classic riff from Eric Clapton. This shows how a simple riff can really be memorable. The way I demonstrate it here is to play it like it was originally recorded, and then I do a version that I saw Clapton do from a concert in the 80s - still the same riff but he harmonizes the beginning notes. Just goes to show you that even if you write a classic riff you still like to change it up sometimes!