If your scope has two turrets, the one on the top adjusts elevation and the one on the right side adjusts windage. If you have two turrets and one is on the left side of the rifle, the scope is mounted incorrectly and needs to be turned to bring the windage adjustment to the right side. If your base mount is not tight and free of movement you will never achieve desirable results, so do whatever is necessary to ensure it doesn't move. The scope rings must be attached tightly to the base and free of movement. The rings should be tightened snugly onto the scope tube, but not so tight as to mar the scope tube or stretch the screws. The best technique short of an inch pound torque wrench is to hold the screw driver between your thumb, index and middle finger with the screw driver pointing straight down from your finger tips. Held thusly, you will be unable to over torque the screws, but they will be tight enough to prevent the scope from moving under recoil.
Move both the elevation and windage adjustments to the center or their travel. To do this turn the dial until you reach the stop, then count the turns until you reach the other stop, then adjust back half way. Now you are ready to sight in.
Take up a solid shooting position at 25 yards. Its best to use a rest of some description, but shooting prone will work if a rest is unavailable. Dry fire a few times to ensure that the scope reticle does not move off target when the hammer falls. If it does you might need to adjust your rest or your position. Now fire 3 rounds at the target. Lets assume your bullets hit the target in a tight cluster 4 inches to the right and 2 inches high of the aiming point. If one bullet lies well outside of the group you need to fire another round or another group. Adjust only in one direction at a time. We'll start with your windage which needs to move left 4".
The windage dial on the right side of the scope moves the windage, and your scope might have quarter minute, half minute, or even eighth minute adjustment. If you have a European scope, each click might equal 1 cm per 100 meters. We'll proceed as if you have quarter minute adjustments as these are the most common. To move 4" at 100 yards would require 16 clicks, but because you are starting at 25 yards you need 64 clicks, or 16 minutes. Your scope adjustments might be calibrated with short and long hash marks. Each of the long hash marks indicates I minute, so you need to move the equivalent of 16 of the long hash marks. Most scopes require that you rotate the adjustment backwards to the direction you want to go, so you would make a clockwise adjustment to move your bullet impact to the left.
If your target is too shot up to easily see new bullet impacts, swap it out for a new one and do this at each stage of the sight in process. Now that your scope is adjusted, fire another group. This should bring you on target, but because the adjustments are not always exactly what they are supposed to be, you might have to fine tune your adjustments with another group or two.
With your windage correct, now repeat the exercise for elevation. You only need to adjust for 2" now, so that is only 8 minutes of adjustment at 25 yards. The scope adjustment is probably counterclockwise to raise the point of impact, but there is probably an arrow and the word UP indicating the direction of adjustment to move the point of impact up. Lets assume you are now zered at 25 yards, so now its time to go back to 100 yards.
At 100 yards you will find that your rifle prints pretty close to where it did at 25. This is because your initial sight in was for the bullet first crossing the line of sight, and now it is falling back across your line of sight. It should take minimal adjustments to get your 100 yard zero, but at 100 yards each click of adjustment equals a quarter inch on the target. So If you need to move the point of impact 1", you only adjust 4 clicks.
Once you are zeroed at 100 yards, you can keep that zero if you are restricting your shooting to 100 yards, but most folks want a 200 yard zero. The rule of thumb here is 2" high at 100, and you can easily do that, while shooting at 100 yards, but it is much better to actually shoot at 200 yards if you can arrange it. You might find that your windage needs to be tweaked again and this won't be evident when shooting at 100. At 200 yards each click of adjustment will shift your point of impact a half inch. Once you have achieved your 200 yard zero, I would encourage you to shoot at 300, just so you come to understand how that much range will effect your groups size and the amount of drop on the target.
