1) The shotgun should fit properly. If that means modifying the stock, get it done. Generally factory SGs will fit a majority of the population pretty much 'as is' but if you are taller than normal or shorter than normal and the gun doesn't fit, alter it to fit. If you have a short fore-end on your gun and you have short arms, get a long field type fore-end on there, and get it slimmed down some so it fits your hand. That way you won't have to extend your weak side arm so much you have trouble supporting the gun.
A good recoil pad helps IMHO. If that means replacing the factory offering, no big deal. I like a rounded toe and a bit of an angle at the heel from the top screw up to help with mounting.
2) Mag extensions IMHO are there to make life easier for the mag spring, not so you can stuff umptyleven shells in your gun and leave them there for a few years. A one- or two- round extension is generally plenty, save for a 'game gun.' I like to load the magazine 'one down' and thereby leave room to insert another round of a different type if needed. In a standard magazine that means I load three rounds. With a one round extension I can load four rounds and still be 'one down.'
Again, you may need to leave the extension off because it adds weight and shifts balance toward the muzzle- that causes some people problems in handling the gun. Gotta have a clamp if you add an extension.
3) Big head safety, I don't like. Too easy to get nudged off, the standard button works better IMO, is easy to get to and easier to determine status by touch.
4) SideSaddle. I like 'em a lot. Other folks hate 'em just as much. Kind of a personal thing, but I like having a reload on the gun all the time and don't find any problems with SideSaddles. They do make the receiver thicker tho, gun won't fit in lots of electric locks etc. with one on.
5) Sling. A gotta- have IMO. Should be sturdily mounted in such a fashion as to not interfere with running the gun (a bunch of sling webbing jammed in front of the forearm can ruin your day when it keeps the bolt from closing). Needs to be detachable so it comes off easily if need be. Lots of options to slinging, can be as simple or as complicated as you like but it needs to be there and it needs to be strong.
6) Barrel. I like 18" barrels on working guns. I like extended forcing cones. I like choke, either IC or MOD and factory fixed is preferable, because I like tight buckshot patterns. I like sights, factory rifle sights are fine, and I like tritium in there too, which means replacing the factory inserts. All those are preferences, not necessities. A plain gun that runs will work.
7) Light. I like a white light source on a gun. I may not USE it, but I like it to be available. I like M3s, they go on and come off easily so they don't have to live on the gun all the time and they work as a flashlight by themselves when off the gun. They don't take up needed hand room in a short fore-end like the SureFire variant does.
Chances are, issue guns will be bone stock. I'd leave it as is for practice for the academy, unless I could find out what the issue guns will have on them there.
Much luck to you, be careful and stay safe.
lpl/nc
