In my experiences I have found they did best drying out then watering well(to soil capacity,with out standing water) I don't think it makes them set faster but in Washington it can get a bit cool during any part of the growing season so its best to let them decide how much water they need (checking on them occasionally) 

Thanks for your replies, I'll check with the old timer gardeners here and see what they say as well and report back.

I am all about watering as little as possible. I have in fact only watered my tomatoes twice since Feb. We have had rain but it has been in the mid to upper 90's with triple digits set to start next week. I have more tomatoes than I know what to do with in my small 100sq/ft garden. One of the benefits of a total organic program is you can cut your watering by at least half and I think I have done a good job backing up that assertion.

I spoke with my Italian 91 year old gardener friend and he said he didn't water a great deal, but that certain larger tomato varieties he gives additional (more frequent) water to. Basically though, he said he waters every three days or so.