either round out the hole or make is square. I prefer to get a drywall saw and make the hole square and to a set inch size per size. Like make the hole a 12 inch square.
Now, get a piece of drywall and cut out a 12 inch square.
screw on the back side of this patch piece, two 1 x 4's evenly apart and to extend about 6 inches over one side and about four inches on the other side. The reason is you want to slide these overhangs in the hole and to overlap the wall on the INSIDE.
one more step. screw a screw into the front of the patch and going into the wood, this will serve as a handle.
Now, angle the patch into place and mark the outside wall where the overhangs will be so that you can screw a screw into the wall and HIT the overhangs behind the wall.
Now, the rough patch is in place and all you have to do now is to tape and mud the square, do the three steps, then sand then texture and walla, its fixed.