How do the techniques for writing for animated cartoons differ from the techniques for other script-writing? Is there a guide for writing for cartoons? I suddenly find myself writing for a flash Youtube cartoon series.
Well, a lot of big animation studios (Disney, Pixar, etc) work with storyboards rather than scripts. Try that.
Have your target audience in mind, but don't stereotype and don't dumb it down. I mean, if that's a cartoon for kids, make it a nice tale for kids, but get the characters a secondary, non-obvious set of characteristics; have them play it through some behaviors, things that kid will simply shrug away as some insignificant discrepancy but an adult will notice as a nice nod - example, a benevolent wise master is secretly a prankster, half of the trouble - the more harmless half - is not random accidents or omissions but caused by them secretly. Make the story layered - the simple, obvious layer for kids, and a second, hidden layer, an implied play behind the scenes for adults that watch it. That truly will make a difference between that being "just another toon" and something excellent.
Also: Learn your animation crew skill level. There are things that will be difficult to animate and draw. Full views of streets of lively, busy city may be impressive but take ten times as much time to animate as a sequence of talking heads. A sideways walk cycle is a standard pulled out of library, three minutes of animator work, but a rich, dynamic fighting scene will need to be drawn from scratch, a week of work for the whole team for a minute of animation. Talk to them and if that's a series, balance their workload by picking enough "rich animation" and enough "filler" so that making an episode takes roughly the same effort and cost.
You can afford some more flair for pilot, season finale, and 3-4 episodes, but prepare 2-3 episodes of "filler" with roughly half of the core crew missing each - voice actors want a little time off too, and this gives them a week or two of holidays.
In essence, if you write a scene, try imagining how it will look like, when done - and then imagine the workload needed to make it. Make it too hard and expect it will be cut by the storyboard artists at request of the director.