The answer, I've found, can be all of the above and, often, a combination of them in a certain order. When working with my manager, as I have been the past few weeks on these ideas, we tend to start off with very general, very short bits of ideas. I'll send him a sentence or two, sometimes without much more than a vague setting, theme, or approach. For example, "Kevin, what about Gladiator underwater; a deep sea diver has to rise up against the king of Atlantis when he is taken captive." Essentially, it's a logline, but it doesn't even have to be that yet. (I'm always wary of giving what I consider to be an extreme idea, since someone out there is likely to see it and want it; if in two years, scuba-Gladiator is on the big screen, please give me a shout-out.)
From there - and consider, we'll do this with a handful of ideas - I'll distill the approved concepts into actual loglines. The goal here is to make them more market ready, clean up the language, decide on protagonists, and make sure they read tightly. Next, we either go to the agent (or producer, etc.) with the loglines or, if we need more, I'll hit the drawing board for a bit and come up with a paragraph or two for each idea. The one or two sentence loglines become 3-5 sentence paragraphs expanding on the concepts, painting the worlds a bit more vividly, and elaborating on the protagonists' goals.
Next, it's off to the agent or producers. The ideas only go out once. If a logline is returned without interest or fanfare, it does not become a paragraph, at least, not any time soon (for now). If the idea garners interest, the outlining phase begins. In recent years, I've really stopped writing without an outline. I find I don't have the time to spend on a draft that wanders aimlessly. That's just me. Some writers manage quite successfully without outlines, storing entire plots in their heads until they write furiously or just waiting to see where the characters take the script. That no longer works for me.
Once an outline's approved, that's when I'll start writing. By "approved," I don't necessarily mean that my reps pour over each outline and sign off on each plot point. I have to like it, for one. More though, at this point, I'm writing a product that other people are (theoretically) saying they will stand behind. If it goes way off course of delves into the realm of "unproduceable," they let me know. Mostly, and I don't always show my reps the outline, this step is to guarantee that the larger picture still matches up with what everyone thinks is sellable.
Granted, you say, I haven't made a sale yet. True, but hopefully these steps will bring that first paycheck about sooner, rather than later.
