Neither Herrera or Williams will ever be high walk guys (one can hope, but experience teaches better).
The key to success for both of them is to discipline their aggressiveness, as Stairs points out, it's OK to attack first pitch strikes you can hit, but not breaking balls out of the K-zone, that even if you make contact, will be likely an out.
It's just a matter of having a plan when you go up to the plate, instead of blindly hacking at everything.
One thing I've noticed with a young lineup, they seem to be taken by surprise when pitchers throw offspeed stuff in "fastball" situations, first pitch, 2-0, 3-1 and 3-2 counts.
They need to understand that in today's game, everyone has video of you, smack a few FBs and don't expect to see any for a few days until you smack some offspeed pitches.