The BFI has a good list of lectures by screenwriters on their BFI Guru. I've only seen the Paul Schrader one, but I thought I'd share while fresh in my mind. One thing he always has before starting is the title and the end.
In summarry, his process is as follows:
Problem -> Metaphor -> Plot -> Oral Tradition -> Outline -> Script
Metaphor: use fresh way to examine it e,g. unexpected gender or location
Paul also shared a few tricks on dialogue:
- Make it non linear
- Read it backwards, this makes it more intrigueing and can reveal ways to increase impact