The conventional wisdom on weight and rep structure is generally some variation on what FD posted above, but as was pointed out to me recently - there's little actual evidence to support it. What seems to be the case is that the best approach is to use a rep range that enables you to try hard in the last few reps, generally 5-15 reps.
As for the number of sets it seems that for novice weight trainers (less than 2yrs experience) one set is as effective as multiple sets, for the experienced WTs 3-6 sets are recommended.
Different people respond very differently to weight training, so it's worth taking some measurements first - weight, body fat, and limb circumferences, and then check again after a dozen sessions, if you find you're getting big and too heavy for climbing you need to try a different rep structure, exercise choice and even if you should be weight training at all.
For exercise choice - 'train movements, not muscles' so keep to compound, multi joint exercises.
A weekly basic routine could be:
Workout A.
Squat (Overhead, front or back - mix it up)
Pull ups
Bench Press
Deadhangs
Core.
Workout B.
Deadlift
Bent Over Row/Tuck Pull-ups
Dips/decline bench press
Deadhangs
Core.
Alternate workouts after climbing twice a week.
You could if you need add in some specials:
Upright Rows, I like these for my weak shoulders and also think they help with forearm extensors.
Tricep extensions, good for deep locks.
Chest flys, good for Font style compression moves.
Javorek Dumbbell complexes are a good intro to weight training
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