I don't follow a schedule for writing. It's not like "Oh, it's noon, I should write for thirty minutes!" or some other set-up like that. I can sit and write for four hours, or spend two weeks doodling on the margins of my paper while trying to find inspiration.
While sometimes this frustrates me to no end, most of the time I'm just fine with it. I'm a rather spontaneous person to begin with (I moved while on vacation, you don't get more in-the-moment than that!) so having bursts of 'inspiration' that come and hit me tends to work fine. Most of the writing I do during that time is better quality than if I have to wring it out of a dry cloth!
I just try to not go too long without writing... a couple weeks or a month is okay, but any more and I'm really pushing it. I have some readers who would gladly hunt me down and kill me if I just quit now. And they are terrifying enough to keep me writing. A certain person with a rather stunning trench coat comes to mind when I think of taking too long, and he's enough motivation to keep my fingers moving.