The Idea Step
Basically, you want to maximise the time you're actually spending coding, creating assets (placeholder or no), and generally actually working on your game. So this step, by necessity, is kind of a short one. I'm not gonna give a number for how long you should be at this (because this is my first LD, and I am, as noted, no expert), but my personal ballpark figure is "If you're at this step for more than 4 hours, something's gone awry."
So let's examine the process a bit...
The Idea Sprang Fully Formed From My Brow
Unlikely, but if something like that genuinely happens? Count yourself lucky, write it down, and use the time you wanted to allocate to ideas either generating other ideas that might be better, or as extra time for step 2, reduction. Either way, yayyyyyy!
Ideas, How Do They F*&!ing Work?
Well, ideas can come from a lot of places. From other sources, from thoughts you have... There are processes that you can use to generate ideas, including keeping fragments of older ideas to bounce off of, doodling randomly/mentally idling until something sticks, or the one I'm quite fond of, the Idea Cloud. I'll explain how it works now.
Yes, my handwriting is godawful. My all-caps ain't much better either.
Okay, here's my Idea Cloud, as written on a £1 sketchpad I've never actually used for sketching. You can see here my thoughts are mainly along the lines of other dimensions, but I'd like to draw your attention to the mention of The Winchester Mystery House (aka The Winchester Mansion). I'm going for a subversion of that basic idea with the game. We'll see if it's too ambitious soon enough.
But it's the stream of thought that matters here, and an idea cloud represents that. All those smaller words around the big theme? Those are ideas. I didn't try to organise too many of them, but it led me to my theme in under ten minutes (I had time, before the Jam, to write a template of this post beforehand, saving me further time.)
The trick, basically, is to channel the consciousness toward something that you think will work. Now for the next bit.
Reducing the Problems
Your idea is great. My idea is at least theoretically workable. But the ancient Engineer's maxim applies in Ludum Dare like no other: Keep It Simple, Stupid. Let's say your idea involves a guy, who lives in this living breathing city, and he can't be seen or heard by people one day, and he can change their emotions to make them do things, and-
STOP. This example is the very idea I proposed to a friend a while back, and he quite rightly told me, as a first project, even as a project for a single experienced dev, this is going to be trouble. It involves a city, for christ's sake. Even a few blocks of a city involves at least a thousand individuals, and you're meant to affect even a hundredth of those folks in contextual, unique ways? Geddoudahere!
Now that you have an idea, it's time to put limitations on it. And not limitations in the sense that you're taking away things you can do, but adding rules, but in the sense that you are literally slicing bits of the concept so it'll fit. It'll feel like butchery, it won't be a grand vision... But dear god, it'll be something you can actually make in 48 hours. While we're on the subject...
I AIN'T GONNA SLEEP!!!
Hah. It's do-able, believe you me, it's do-able. I made 72 hours more than once, but believe you me, I was pretty squirrely by the end of it. 48 hours is actually much less of a proposition. But if you don't at least nap, your work is going to suffer. You'll make dumb mistakes, which introduce bugs, which you then have to spend time fixing. Take breaks, this isn't about "Who's the best at karoshi" (remember that series? Boy, that was a riot!), it's about managing your time efficiently, and improving your practice by introducing limits. Unless, y'know, you enjoy that sort of thing, then go hog wild. Another environmental factor?
OMG, IT'S [INSERT FAMOUS DEV HERE]!!!
Doesn't matter. Seriously, while this has stopped me before, two years of reviewing has led me to quite confidently say "It doesn't actually matter." Why? Because they're people, and, like any people, they're going to have hassles, mistakes, bugs, setbacks, and, if they're doing the no-sleep thing too, the occasional period where they'll zonk out and suddenly say "ARG FUCK, TEN HOURS? AAAAAHHHHHHH!"
I've said it just a few short paragraphs ago, I'll say it again. It isn't about prizes (are there any? I forget, and don't actually care that much...), it isn't about who's who (although friendships made at Jams and during the dev process are a nice addition), it's about improving your practices, your game. I just saw Michael Hitchens, a name I'm sure I've seen in the SA GameDev thread at some point, and my reaction?
"Oh, cool, look forward to seeing what they make!"
Before I get back to creating placeholders and scripting (I touched this post up in my first ten minute break), let's talk about my own personal flaws with practices. Well, the ones I'm aware of right now.
Accepting I'm No Angel
Procrastination. There's a good one. I procrastinate, mainly because there are many cool and shiny things for me to do and play with, it's easy to distract myself. This blog, for example. If I'd written two thirds of this entry in the middle of LD30, I'd have wasted half a damn hour, at least. Sounds bad, but assuming I write more than 6 of these (same length) during the compo, that's 3 hours for sure, and that's 3 hours I could have spent polishing my game till it spangles like a figure skater's leotard.
Frustration. Like any human being, I get pissed off when things don't go my way. This can happen with what I later see as perfectly serviceable ideas, because fuckdammit, they're not coming out of my brain onto the computer magically like I want them to!!! This is where iteration comes in, by the way. Start real small, work up. That way, you won't get so pissy when it isn't automatically working, because you expect it to. Let's see how well I hold up with that in the next twelve hours or so.
There are other flaws, I'm sure, but those two are probably the biggest blocks, and ones I'm determined to get past. One thing's for sure, I've been hype since I woke up, and since depression is a problem for me, that's ultra cool!