Ensure there is minimal difference in temperature from the exterior (outside) and interior (inside the attic) to prevent condensation on the underside of roof sheathing.
Attic air seal all points of entry such as (bathroom fans and hoses, recessed lighting/ pot lights, use low temperature light bulbs (LED), install or fix weather stripping around attic hatch, seal around holes, gaps, and cracks inside the attic including wiring, plumbing vent pipes, or ducts (in some cases).
Ensure all rafter ventilation/ baffles are not damaged or blocked with insulation.