RE: Offhand shooting techniques
The best thing you can do is put a sling on the rifle and learn how to make a "hasty sling." Go down to your local guns shop or club and as somebody to show you. If you know any Marines or soldiers, they could show you too. I'd try to explain it, but I'd probably confuse you. I've also seen the occational writeup with pictures on sling use in at least one recent gun magazine. It'll help a lot to steady your shots.
Other than that, shooting offhand is where all of the fundamental marksmanship skills play their most critical role. If your stance, aiming, breathing or trigger control, or combination thereof, aren't very good it'll show downrange shooting offhand. Practice is also very important, but all the practice in the world with crappy technique is an exercise in frustration in most cases. It is unfortunate that there aren't more affordable courses and instructors across the country to teach civilians basic rifle marksmanship technique. I can say that spending $250 on an NRA Rifle Course would be money well spent if you can find an instructor. I've often said that my dad taught me how to shoot a gun, the Marine Corps taught me good marksmanship and made me a rifleman. I was amazed when I realized just how bad a shot I was before I received formal training (though I wouldn't admit it!). Some people have a natural talent, but most of us benefit tremendously from training.
And lastly, don't get discouraged when you're not able to shoot as well as you'd like at first. Shooting offhand precisely is tough, especially when then range gets out to 100 yards and beyond. You'll hear stories, and read a few here from time to time, about someone who can put a bullet in a deer's ear canal at 300 yards from the offhand every time, how "easy" it is, and how anyone who can't has no business in the woods. Don't believe it, as almost all of these people are full of s***. If they weren't, they'd be untouchable world champion NRA High Power shooters. Realistically, if you can hit a 6" circle at 100 yards every time, you're doing a lot better than most, and if you can hit an 8" paper plate and whatever range all the time, you're good-to-go for all shots at deer or bigger at that range. Practical marksmanship is not about shooting tiny groups, it's about hitting what you're aiming at well enough to achieve the desired result.
Practice hard, shoot straight and good luck.
Mike