Make sure the gun is set up balanced so it sits in your should and rests on your hand wit out having to "hold" it. Gemini Butt hook helped for me. The Njr is a heavy old baest!
Biggest factor tha improved my standers was a Gimp coat however. Went from hitting 1 in 4 to 3 in 4, most days.
Saying that, I think the coat helped me practise and get my overall technique correct for standers as well, as I have shot lighter guns (ev2/ Walter) with out the coat and been just as steady.
Practise, look at photos of yoursef standing, compare with the likes of Ozbourne or the best shots in your region and adapt there techniques to suit yourself.