Most shooters do not actually know if their scope’s adjustments are accurate. Just because the manufacturer of the scope advertises each click to equal 1/4" @ 100yds doesn’t mean that scope actually moves 1/4" every time a click is made. Scopes sometimes move more or less than advertised. For example a scope advertising 1/4" clicks at 100 yards should move 1 inch for every 4 clicks but often may in reality move only 3/4" per 4 clicks or as much as 2" per 4 clicks. Therefore counting clicks to adjust your scope often isn’t very effective.
The correct way to zero your scope in far fewer shots and to avoid counting clicks is to proceed as follows. This method works whether or not your scope turrets (adjustments) actually move their advertised amounts or not.
First, if your scope has just been mounted on the rifle and not previously sighted in, place a target at 25 or 30 yards away. This step will be necessary even if the rifle has been bore sighted. From a steady rest using sand bags to support your rifle, fire a single shot at the bullseye of the target. After firing this shot locate the bullets point of impact on your target. You will probably be able to see the bullet hole in the target through your scope. Now, remove your scope’s turret caps and place them in a safe place. Line your rifle back up on the bullseye as though you were going to fire a second shot (just as you did before).

Without moving the rifle, turn the adjustment knobs (turrets) of your scope until the crosshairs are on the bullet hole. Your scope’s crosshairs are now adjusted to where your rifle’s barrel is shooting. It is much easier to perform this task when you have someone to help by either holding the rifle perfectly still or by turning the knobs while you hold the rifle still.
You can now move on out to 100 or 150 yards and go through the same procedure. More likely than not, you will have to do some adjusting as you move your target out. If you want to be zeroed in at a longer distance repeat this process moving your target out just 100 yards at a time. Moving out in 100 yard increments will keep you on the target paper as you work your out to your desired zero range. You should only have to fire 2 or 3 shots at each distance in order to have your scope zeroed in.
Another factor that causes shooters difficulty sighting in is the fact that many of them fire too rapidly. This causes barrels to overheat and in turn causes shots to fly wildly outside the rifles normal group size. Shooters will many times adjust their scope thinking a wild shot is actually where the rifle is shooting. Slow down and give your rifle’s barrel time to cool down. Doing this will keep flyer shots (shots that stray) from happening so often. After all, in a real hunting situation your rifle’s barrel is going to be cool when you shoot.