I like 18/6 but some people stay 24/0 for the whole grow. I think this hurts terpene development and doesnt give you any noticeable benefit.
Make sure you use a lot of P and K while cutting down the N.
Harvest by hairs: when 70%-90% of hairs are red, longer you wait, the more body high you get.
Harvest by amber trichome:
10% for energetic mind high
20% mix of above and below
30% couchlock
50% prescription strength sleep aid
Use a jeweler's loupe of really good camera to check trichomes, loupes are cheap.