The post on this thread have all been right on the mark, so to speak. Let me see if I can add a few tips that may have been left out.

First, control your breathing. You want to squeze the trigger at the end of your exhale. Also you want to control your excitment...the more excited you become the more your heart pounds, and (believe it or not) that will effect your aim.

Second, (and this works really well for me) use only the tip of your finger on the trigger. The natural motion of the human finger when you curl it is to pull to the inside of the palm, that's to the right if you are right handed and the other way if you are a lefty. using the tip of the finger (from the last knuckle up) helps solve that problem. Your finger should be almost strait before you put pressure on the trigger. Also have your trigger pull adjusted for a light pull.

Third, wear hering protection!!!!! The krack of the rifle will instill an automatic reflex action in you that will throw off your shots. You will never see anyone in the military or the police on the range without them.

Forth, the more rounds you fire through your rifle at the range the more comfortable you will become. I go to the range 4 times a week in all weather conditions so that I will KNOW how my rifle and I will preform under any conditions.

Lastly (unless someone brings up a good point) never fire your weapon at a moving target at the ranges that you indicated. Chances are that you will miss and the only thing you will get out of the deal is to change it's direction of travel, making it harder to pick up it's track after you come out of the stand. That's happend to me more than once and I still get pi**ed just thinking about it.

Try these things with the penny trick at home (DRY FIRE) and see if they help

Good luck and let us know how it works out.