First step is to handle as many O/U as you can. You will find a manufacturer that makes a stock that fits you out of the box. It may not be the manufacturer you were planning on but .... For me the Berettas and Brownings were nice, but didn't fit me well. I ended up with a Caesar Guerini that fits like it was made for me. Definitely more dollars than I was planning on spending for a hunting shotgun, but I can't take it with me and it is my retirement gift to myself!
I also have an older SKB 500 that fits me excellent. Don't overlook an older O/U as there are some beauties out there. I would stay away from most Turk O/U or SxS as I have had issues with most and all are down the road.
