How many sets?

[Slyder190]

I've been reading through Charles Poliquin's "Modern Trends In Strength Training". He mentions that at reps of 5 and under, many multiple sets can be used. What is an average for say back and tri's and bi's? I'm using one of his routines right now, but not sure how many sets to do. I did 12 for back (not low back) and 8 for bi's and 8 for tri's. He also says routines with reps of 6 or more require less sets. I will be switching back and forth as I want power but size as well. How many is too many when doing 6 or more reps? Thanks.