Like previously stated go pattern your shotgun with the loads you intend to shoot. IT IS THE ONLY WAY TO FIND OUT HOW YOUR GUN IS PERFORMING WITH A PARTICULAR LOAD.
When chosing a choke the general rule of thumb is you go down to a more open choke when shooting steel. If you want a I.C. pattern put in SKT, for Mod use I.C. ,for Full use Mod. To my knowledge most shotguns in the last 25 years are safe for steel when you're talking production guns like Browning Beretta,Remington etc etc.
In most cases anything tighter than modified would be marked "not for steel" like your full or ex-full chokes.