Most people will get good results following Joihn's guidelines.
My addition would by, after you've gotten your "bench screamer" group, try shooting it as it would be in the field. Whether it's pack, bipod, a handy bush or whatever, that's the real test of your setup -- and you. I'm pretty good at "benching" but honestly pretty lousy when it's for real. But I'm okay with taking all the blame for a rotten shot.
