Watch the Carl's Shuffle 3 online guitar lesson by Carl Verheyen from S.W.A.T. Blues
The shuffle feel is explained in this lesson. The difference between duple meter and triple meter is an important thing to understand, and a huge part of your conceptual ability to feel the groove correctly. It can't be done in duple meter as you'll see in this lesson. The next concept to grasp is the ability to pinpoint where you're putting your part against the time. Are you ahead of the beat, behind the beat, or do you play center time? Once you understand this you'll be able to lock into a drummer's heartbeat. Every drummer has a different feel, so this is very important whether you're playing rhythm or lead guitar.