The most important thing is knowing what your dimensions are and what fits you. Don't stay from it or else it will not be the gun for you.
If you have something now that already fits you that you shoot well, try to copy what that gun has in whatever you buy. Doesn't matter if it is just some Mossburg 500 or a plain old single shot. Last thing you want to do is spend a bunch on something that you can't hit anything with, or have to put more into it for stock modifications and such.

B.Dudley