It's just a matter of finding a good patterning load...then adjusting the cross hairs to where you want it to be..You have to find the center of your pattern...at your preferred yardage..Adjust the cross hairs..or circle depending on the model of scope to cover the center...
A old trick to find this was to take a twin white bed sheet and pace off the distance you will shoot at...Fire about ten shots into the sheet and you will see the center of the pattern...it also holds up to repeated shots to the same area..You can measure the distance as well with a laser range finder or optical range finder...
Adjusting the scope to this is best done off of a bench and having a gun vise...same as a rifle scope...but you can get by using a somewhat large cardboard box...and cutting a couple slots in each side to hold the gun in...and carefully adjusting the scope to the center of the pattern...Different chokes will effect the pattern naturally...so you will want to try different loads and see where the center of the pattern is at various yardages..Since most turkey hunting is done sitting down...setting up a scoped shotgun barrel is best done this way too...It's really the same as a scoped rifle...so it won't be much different..I bore sight mine prior to going out to the range...doing so will help get you on target quicker...
The main thing is knowing how it shoots a the different ranges...and where the pattern opens the most to not allow multiple hits to the head neck area..The more hits..the better...
I did find another link for you...
http://www.conservationcafe.com/Hunting/article_detail.asp?iArticleID=40Mac
