Sighting in

[cka122]

I'm  sighting in my benjamin trail np and I wanted to know what is a good distance to sight it in at?

[Bullit]

It's much easier to work with 20 or 25 yards, than 10 yards.  Gives enough distance, for the barrel and pellet, to "rise up" to meet where your scope is pointed. Optically center your scope to start.  Shoot a few patterns to see where you're hitting before chasing the shots by cranking on the scope.

[Airgun.Sniper]

Id start sighting  scope  in at 10 yards then on to 20 yards.

[Bullit]

Cranking a scope upwards, at just 10 yards is problematic for the health of the scope (unless this is your target objective, or course). 
If it's on paper, and "low" by a few inches.  Don't worry right away.  This is natural with the heigth differences between the scope to barrel centerlines.  It takes yardage to make the 2 lines to intersect.

[Yarp]

Post targets at ten, twenty, thirty and forty yards.
Sight in on twenty and then shoot at ten, thirty and forty.
Play it by ear from there.

If you've got all day, post every five yards.