Growing up I always did the 25 yard sight in. I was shooting mostly groundhog and squirrel. The chart below is what 2 well know gun writers recommend have put out. They say 75 yards. But, I believe the best way to do it is hit the range and use some different 22 shells. I don't risk shots on squirrels in trees over 50 yard unless I have a hillside as a back stop and even then it's not worth the risk just for a squirrel. But I do like eating them.
RWS Subs zero at 40. Puts me right in at 25 and 1” low at 50. All this depends on your scope height. A 22 trajectory isn’t flat and you will be surprised how much scope height affects impact between 15-40 yards