Hey Goose -

As far as solidifying ideas - I know that a lot of people do the index card thing...but that just doesn't fly for me.

Best thing for my M.O. is to start brainstorming (purposely without structure, to allow my subscious room to breathe) while typing in Microsoft word.  

As stuff starts to flow together, I classify it into the various appropriate sections and keep building.  Lines, character backgrounds..plot ideas...

Great thing about Word is that you can cut and paste and move stuff constantly.  It evolves.  I make sure I've got ALL that nailed down before I ever fire up Final Draft.

Works for me.  Polishing a sixth feature length right now....  

For my original feature screenplays  it's...

Brainstorming & taking iPhone notes while power walking in my hood.

Assuming it gels, then I step it up to story beats and possibly treatments.

Assuming it still excites me, then I'll outline/corkboard the stuffing out of it.

If I can't shake the idea through all those steps, I'm thinking others might dig it too.

And if I'm still not bored with the story, then I'll write the screenplay.

E.D.

I've done cards, beat sheets, what have you, and, depending on the story, still use those tools some, but, at a certain point when three-act structure is second nature and all, I just start watching the movie in my head and I keep rewatching it until it's the movie I want to see.  Then, write it.  I have a pretty strong memory, otherise so much would get lost.  if you're newer to the craft, notes, notes, notes.