Rifle enthusiast now use rifle scopes more than ever on most of their guns, not just their rifles, and the reason is simple. Lining up targets with a scope is easier than doing so with regular iron sites.
In order to use a rifle scope properly you must first start out by getting the right rifle scope. You must understand the lighting, distance, and the target you're trying to hit. Getting the most powerful scope on the market isn't necessarily the best idea. Your field of view could suffer and a target that is only yards away may come out blurry. So understanding what you are going to use the scope for and in what conditions is a highly important step in choosing the right scope.
Next you must "site in" your scope. Sighting in your rifle scope requires use of a boresighter and requires you to shoot your gun during adjustments. No boresighter, even a laser boresighter, will get your scope sighted properly without shooting and making adjustments. You must also do it for each rifle even if they are of similar make and model. Each rifle is unique and must be treated as such.
While using your rifle scope during sighting also take into consideration the ammo your gun uses. Different types of ammo will result in different outcomes. The same ammo in one rifle may not be as accurate in another same make and model rifle. Different lot numbers of ammo will have different outcomes as well so sighting your rifle will be a common thing you do even after purchasing new ammo. Once again it is important to treat each rifle in a unique way to get the proper results.
Bullet Drop Condensers (BDC's) are turret adjustments matched to your caliber and bullet weight. They work by having you gauge the range to your target then by adjusting your turret to the distance marked on it. Most drop condensers match common military calibers and use the weight, or grain, of the bullet you are using. While they do make a difference they are not perfect and must be calculated for each rifle as well. There are many factors besides just distance and weight that help get you on target Temperature, elevation, humidity, and barrel cleanliness to name a few. BDC's can get you close but it is your skill that will get you on!
Use your rifle scope wisely and you will win!