Sighting in a rifle should not be performed once and never thought of again. Just bumping the scope could throw your rifle's alignment off, so you should zero your rifle fairly frequently to accommodate changes in your own eyesight, or a new scope or barrel, or just to make sure it is still shooting true.
Shoot from a bench rest, if possible, where you can rest the muzzle on a sandbag or other steady support. Reducing the waver in the rifle barrel is critical to accurate sighting.
Use the prone position if a bench is not available. On the range, or a spot cleared of rocks and sticks that could interfere with your position, lie flat at a comfortable angle to the target, as close as possible to the natural position you would always take when shooting.
Use a sling to help steady the rifle against your arm, or rest the barrel on a sandbag.
Plant your elbows comfortably on the ground. If there is a twig under the point of your elbow, move it, as it could cause your elbow to shift.
Snug the rifle as tightly into your shoulder as possible.
Look through the rear sight or scope, and make sure the position of your head is natural and the sight picture is clear. It should imitate as much as possible the angle you will always use when hunting or target shooting.
Make sure your scope is focused, and set it to the highest power that allows you to see the target clearly, giving you the best sight picture possible.
Bore site your rifle at 100 yards by removing the bolt and looking through the barrel at the target. Without moving the rifle, adjust the scope so that you can see the target through the scope. This provides a rough "bore-sighting" to use as a basis for fine-tuning.
Start at 25 yards. By starting close, the bull's eye will look bigger and is easier to hit, and adjustments are easier.
Move the target to 100 yards when you are certain your rifle is shooting accurately at 25 yards.
Make sure, if you are not shooting on a range, that your targets have a proper backstop and that you are not shooting uphill or in any direction where a stray bullet will hit a house or a hiker. A 30.06 is accurate to over 1000 yards, and the bullets will carry much farther.
Sight your rifle at 25 yards for true center, both for height and for wind; at 100 yards you will be sighting it to shoot two inches above dead center and dead on for wind (when you aim at the bull's eye, a properly sighted rifle will shoot two inches above it).
Look through the scope and line the rifle up dead center on the bull's eye. To make sure you are not straining to hold the rifle on target, close your eyes for a few seconds before looking through the scope again. If the muzzle has drifted off target, likely you are manually holding the rifle in position rather than letting it rest naturally.
Check each round through the spotting scope as you fire, without changing your position, to obtain complete accuracy. If you have no spotting scope or can't see the holes through your rifle scope, you will have to get up and examine the target, but fire a few rounds first without altering your initial position.
Keep track of each shot on a paper target on the shooting bench, to take the guesswork out of where each shot landed. Number each shot fired.
Try to "call" your rounds by noting where the crosshairs on the scope were positioned when the round fired. If the actual bullet holes don't match where you think they should be, your sights probably really are off.
If you are pushed for time, use the military style sighting method of three-round groups. Fire three rounds at the bull's eye without stopping to adjust your sights or moving your position.
Check where the rounds hit with your spotting scope, again without moving position, if possible.
If the shot group is reasonably close together, use the center of the group to determine how far to move your sights for height and for wind. If the shots are scattered, shoot a second group and try to control your breathing.
Once you have determined that the rifle is shooting consistently, whether or not it is on target, move the sights in accordance with the directions that came with your scope. Different scopes may use a different number of "clicks" to achieve a particular movement over 100 yards. If it takes four clicks to move the sights one inch at a hundred yards, it will take 16 clicks at 25 yards to move it one inch.
Fire another round to check the accuracy of your adjustments. Your goal is to put it within the 10 ring at 25 yards, or at least within an inch of center.
Continue to refine your sight adjustments as necessary, until you get a consistent three-round group in the center of your 25-yard target.
Move to the 100-yard target and repeat the exercise, striving for a natural position, steady, controlled shots, and a sight picture that matches the holes in the target. If you can call your shots and the call is borne out by the target, your rifle is shooting accurately, and any wild shots are likely caused by you.
If your shots refuse to line up on either target, check the mountings of your scope to see if it is being thrown off by recoil or drifting slightly.
Verify your zero every time your rifle has been unfired for a long period of time.