I wish I had taken photos of this process, but I was doing it on the fly while babysitting a friend's daughter on Saturday, so I didn't achieve photos!
A couple of weeks ago I bought a few dresses; one of them was the "casual weekend dress" from Boden (in Lavender Grey Woodblock). When it arrived and I tried it on I realized that it was perfect except that the bodice was way too big on my short-waisted physique, resulting in a very low-cut neckline and unattractive "bagginess" throughout the bodice.
Here's how I fixed it: I put the dress on my dress form and played with it. (My dress form is a replica of me: SO HELPFUL.) At the shoulder there is a narrow panel and the front and back bodice pieces are attached with some gathering to that panel. I took my scissors and cut the panel--just sliced it open! Then I just lifted the bodice until it looked good, pinned it, and sewed it all shut--right sides together, of course. The back side was larger than the front side. I didn't do any formal gathering to eliminate the extra fabric; I just put a couple of little tucks in as I sewed along and no one is the wiser. Now the dress is perfect, the neckline is at the right place for my comfort level (I do not like a low neckline), and I didn't lose my armscye (a big concern). I cut the excess fabric out of the seam-there was a lot--and tacked it back so it looks nice. The binding on one side is a little odd, but I'm not worrying about it.
I still cannot believe I had the nerve to do this, but I'm glad I did because I wore the dress for Easter with a white cardigan and my favorite linen-cork Etienne Aigner peep-toe wedges. Yes!
Fortunately the other dress I bought only needs to be tacked at the crossover front for the sake of some modesty, and that's easy!