If you want the short answer, go read the F chord post and move it up 3 frets. IMHO it looks like this at its best:
-x-
-x-
-5-
-6-
-6-
-4-
You should be able to do this all day long. Occurs to me that you might see it’s resemblance to a power chord as well as a barre chord, but it’s somehow neither, right? I KNOW! that’s what makes it rock. The note on the G string, in this case C natural, is the major third of the chord, giving it the quality of being major, yada yada… Anyway, this is a great way to throw an Ab chord ito your vocabulary.
Now the fun ones.
-x–x–x
-1–1–1
-1–1–1
-1–1–1
-3–x–3
-4–4–x
So there’s three more. These are pretty easy to grab, very grokkable, and sound more like a cowboy G chord without cramping up your hand or forcing you into a full barre chord.
For the first and second voicings out of these three, I’d suggest grabbing a cowboy G chord with your 3rd and 4th fingers on the two lowest notes. In this case you won’t be using your 2nd finger for anything, so try not to look like you’re flipping the bird at your audience. Try and keep it low, near your first finger which is barring the B, G and D strings.
The only variation in the second voicing is the lack of the note C on the A string. The voicing is still major though, since we have a C note on the B string, first fret. This one might be faster to grab though, depending on the situation you’re in.
The third voicing however is definitely my favorite. If I’m not in the key of Ab, or I’m on the last couple counts of and Ab in a progression, I’ll grab this one. It creates a sense of a moving bass line, and I think it’s just pretty. You’d see it on a chart as Ab/C, but that doesn’t matter. It’s pretty rare that a slash chord really matters on a chart. I should probably write about slash chords sometime. They blow the beginners’ minds, and annoy those of us who were planning on doing them anyway.
Play well, you guys.