Robert A. Heinlein: Rules for Writing

1. You must write.
2. You must finish what you write.
3. You must refrain from rewriting, except to editorial order.
4. You must put the work on the market.
5. You must keep the work on the market until it is sold.

See the full post on Heinlein's article from 1947 here:
http://www.deanwesleysmith.com