I just lift to eliminate "gorilla posture".  Shoulders and back one day, chest one day and arms if I go a third time. I do 3 sets of 15 at 4-6 stations alternating pushing and pulling.  I try not to do very much weight at all.  Do abs every time sets of 30 or failure. Warm up with 30 mins on the treadmill at max tilt. I mostly lift in the winter as it definitely does not raise my climbing standard while I'm lifting. The main benefit I see is a complete lack of neck pain since I started and the pack does not wear me down as much.