The middle ring on triples is set up to be used across the first 7 or 8 cogs, although the higher gears are often duplicates of middle-cog gears on the big ring. That's on the high side. On the low side, you're fine. The granny ring you don't really want to use above the 3rd or 4th cog. With the other two rings, just avoid the extreme crosschain gears as if it were a double.

--Shannon