A couple of Saturdays before everyone came up to help, my wife helped me stake out the site where the barn would lay. We had picked up some string and measured off 24x30 and tied the string to the stakes that we had driven in the ground. Then we measured the X in the middle to make sure our two hypotenuse were the same. We adjusted our stakes to make sure they were equal...or so we thought. I placed a 1"x1" stake at every spot that I would need to dig holes for the 6"x 6" pressure treated post. (They are actually 5.5"x 5.5".)
The Saturday before my wife's family came up from Florida, my Dad, brother and a friend came over and we dug the holes for the post to sit in. I went to town early and rented a 3 pt. auger from the rental place for around $35. Dad brought the Kubota over and we started digging. Renting the post hole digger was definitely worth the money. We had 12 holes to dig and it didn't take but an hour or so. The stakes I had driven were used as a reference for the auger tip. The tip would be placed where the stake had left a hole in the ground when removed. (I measured and drove the stakes that way on purpose) We dropped in the post as soon as we'd lift the auger from the hole.
Our first problem arose when we started digging and I didn't double check my initial measurements until AFTER we finished digging all 12 holes. I assured my helpers the holes were layed out perfectly so we just kept digging. Our corners were a little out of square. Ok, 7" out!! How did that happen? Still not sure, but it didn't take long to find the wall that was out of square and move a few post around. Of course we had to do some hand digging though. It was all part of the education process. Next time, I'll dig a hole, then measure, dig another, measure again.
In case you are wondering, I didn't use any concrete in the holes. This hard Alabama red clay is just that, hard (just add water).