I don't think there is any "right" answer for during your cycle. Some folks take 20mg/day during a cycle to ward off gyno symptoms and excess water. I don't run nolva during a cycle unless I start to get sore/ichy nips. THis has never happened to me DURING a cycle. But it HAS happened after a cycle twice as a post-cycle hormonal rebound.
As for clomid and when you should start. Look on the PCT board, I posted a schedule that addresses that question.