The easiest way to reduce recoil is to lighten the loads you shoot. Rreducing the weight of the shot and/or the velocity of the shells will reduce both felt and measured recoil.
Another way is to add weight to your gun.
Both of the above assume that your gun fits you, which is not at all a safe assumtion to make. "Shooting form" (gun mount, body posture) has a major affect on the recoil that is felt by the shooter. Of the two, gun mount is probably the most important.
There are two types of recoil that bother shooters are recoil to the face and recoil to the shoulder. Guns should be mounted in the shoulder pocket just inside of the sholder joint (not the upper arm or shoulder joint).
The causes of objectionalbe recoil to these areas vary. It can be due to a poor gun mount or a gun with stock dimensions that do not fit the shooter's particular size and shape and make a good gun mount impossible.
There are some good recoil dapening stocks and stock devices available but none of them are cheap. The mercury units that fit in the stock bolt hole don't do much more than an equal amount of weight added to the stock. Of this type of unit, the "Dead Mule" seems to enjoy the best reputation. Whether they are worth their modest cost remains questionable, however.