Like Bigbulls said, start at 25, then 50 and finally 100yrds to get it zeroed. I always sight in at the highest power, and then change to lowest and recheck it, although now days it isn't supposed to change zero at different power settings. For the most part I usually set it at what power I would normally use, and leave it there anyway. I did have an old 3-9x that I left on 9x and it jammed there, so as a habit I turn it to the lowest setting when I clean the gun and put it away, probably doesn't make any difference where you leave it, but the old adage is that you should leave a hunting rifle's scope at the lowest setting and turn it up if you need to.