it happens, john, it happens. again, were it a problem in fiction, that would be good reason to come up with an outline and stay on course as well as you can. i personally love the tangents and don't outline, but that works for me. or at least i think it does.
there are so many ways to get distracted and veer away from what you originally had intended. but, there are many ways to stick to that main idea, too.
to actually *answer* your question, kristy, what i do when i'm out of my comfort zone is simply research. i can only speak in terms of fiction writing at the moment, but i think the same holds true for each ~ you have to read (watch) what's in the genre and pay attention like a writer and not look at it from an audience point of view. that is, the audience doesn't need, want or care why something works, but you need to know that stuff.
and you need to know your target audience. if you don't provide them what they want you're screwed anyway. what kind of movie do you want it to be?
i always think in terms of templates. you add this template and it's got part of a roadmap. add another and more of the path is revealed. now, i'm a hack, so this whole template business may seem a bit easier for me. for example, i know that one rom-com is basically not terrifically different from another ~ what changes is the premise, and most of the time even that is predicated on the characters' occupations. i think we all know what has to happen in a rom-com, don't we?
you know what needs to happen in a dramatic love story. you probably have a premise and a theme and a logline. you know all about character arcs and whether or not you want them. you know all about character development and subtext. in fact, you certainly know a helluva lot about the story than you might realize, or at least about the characters and plot and what has to happen.
for me, the initial concept begins with a mix of the character and his occupation. combined with the genre, there's a huge template right there. i also know how i write and what entertains me, but i have to balance that out with the target audience's expectations. i never realized i thought about B stories in fiction, i considered it adding another genre but to a lesser extent (which usually turned out to be romance of some kind). usually for me the setting is implied, but when it's not, or is itself part of the premise, it's whatever interests me personally.
note that i could have written that romance had i really wanted to. the problem was a developing lack of interest in it. and guess what? i don't see me ever doing a project i wasn't interested in again. i know what will happen. it won't be because i can't do it or am afraid of missing a detail, rather i realize by now that experimenting with an idea is fine and dandy... but it doesn't tend to produce results. after all, it's not like i'm going for a grade here. and just because a producer calls you up and wants a draft of so-and-so for something you aren't interested in doesn't mean you have to do it. i mean, is it going to hurt you more turning down a project or turning one in that sucks? (really, though, i don't know why a producer or agent (whomever it may be) would ask this of you unless you give him an indication you can do it. does it bespeak that you're not a consummate professional just because you can't write every single genre known to man? i doubt it.
when out of my comfort zone for whatever reason, i rely on what makes things entertaining to me. for a script, i'll have a logline and theme (probably) (maybe) to keep me in check. ...and to fall back on when i come to a bump in the road.
i'd imagine most of us come to a screeching halt on ocassion then try desperately to find a way to get things kickstarted. i think sometimes we need to be reminded of all these great tools we've already set in place that act like guides. and even then there are times when we just have to wing it and, gasp, use some imagination and creativity even if it might possibly go against the grain just a bit.
as i just walked by the t.v. to ring up a customer, i caught sight of a pair of lovers running through a green field and into each other's arm. puke. there it is ne'ertheless, the idea being that whatever you do to get yourself over a hump probably won't be worse than that old embarassing saw.
the most important tool for writing? in my opinion it's confidence. i know that whatever i write that there will be people out there without any standards whatsoever, so i can just let 'er rip to a certain extent.
does that begin to answer your question, kristy? cuz it seems to me no one ever really did answer it, lol.