I would take 100mg on day one and continue with 20mg/day until starting Clomid.
The reason for 100mg on a first day is because of 5 days half life.
The reason for continuing for the rest of the cycle, is to avoid estrogen rebound, which, most likely will occure, if you stop using it, on a middle. Nolvadex simply prevent estrogen from binding to ER, so it will build up and if you stop will hit your friend harder.