Basically, here are recommended tip from a group (not from each person):
 

Climbing - Chief Guide guide: $10/day
Assistant guide: $7/day (for each assistant guide)
Porters: $4/day (for each porter)
Cook: $8/day.

All US dollars in cash

Safari - Driver: 15/day

Cook: $7/day.

All US dollars in cash

Of course you can pay more if you are particularly impressed and less if you are not.