I like gleaning ideas from various sources and knitting it all together into a cohesive working theory that gets altered as you go along and find out what works best. From Watt's "The 90 Day Novel" I learned about holding an idea loosely and just playing around with it for a few weeks before committing anything to paper, and letting the character drive the action. I got my first insights to how to technically write a script from Field's "Screenplay". Vogler's "The Writer's Journey" gives a great understanding of mythic archetypes and where to best utilize them in a three-act structure. And Iglesias' "101 Habits" interviews a couple dozen working screenwriters and gives some incredible insight to writing and working in the industry. And since I have them all as computer-searchable e-books, I know that none of these books makes a single mention of the word 'logline'.
"Save the Cat" has some great insights into structure, I'll give it that. Making sure you have a theme, making sure you state it, dark night of the soul, the all is lost moment - all good stuff. I'm less committed to his ideas about genre (another thing that irks me about his devotees) and logline. I like a good premise/concept that will eventually grow into a great logline once you know what your story actually is, but for now I think it's actually doing more harm than good as far as my creative process is concerned.