Simple enough? I think the C chord, by far, has the most potential for variation using pretty easy fingerings. We saw three different variations on the last page, but from here on in, we'll only see one or two variations for each of the other chords.
For our A chord, we can remove our 3rd finger, which normally rests on the 2nd fret on the 2nd string, and play the 2nd string (the B string) open. By doing this, we create what's known as a Sus2 chord. Can we all say that together...? "Sus2..." Here's how it looks compared to our original A chord:
The Sus2 chord is another great device in this style. It's similar to the Add9 chord except that an Add9 chord also contains the 3rd of the chord (in the case of an A major chord, this note is C#). When we take our 3rd finger off, we are actually taking it off the C#. Our C# becomes a B (the open B string), and now, because there's no longer a C# in our chord, it becomes an A Sus2. (Yes, I'm aware that this may be more than you wanted to know).
Listen to this variation below. I've included a strumming pattern to show it more in context. Also note that it you arpeggiate this A Sus2 chord in a particularly way, you obtain the opening to "Behind Blue Eyes" by The Who....