That is the question isn't it... lol
I'm new at this so it's going to take some trial and error (hopefully less error). I heard a great podcast a while back that talked about all of this stuff. It was one of the sunday sessions from 2006 and it had Vinnie Cilurzo talking about hops.
Obviously it depends on climate (hot or mild etc.), but I think he said you want to drip around 1-2 gallons per day. The soil should stay moist with definitely no pooled water.