Buy the book Chemical Muscle Enhancement. It will answer alot of your questions.
Nolva is generally used during and post cycle and it is to block estrogen. Clomid is used post cycle (about 2 weeks after your last shot if you are using something like test-e) to get your brothers working again.
I never do a cycle anymore without some HCG on hand. Also during a cycle I will use a-dex which will reduce or eliminate the need for Nolva.