Where do you do most of your plotting? At your desk? Eating dinner? On a long run?
Since my devoted writing time is limited, I have to force myself to think about my book throughout the whole day. The best times are when I'm cooking, folding laundry, nursing, or in the bath. (For some reason, the bath tub is the best place for me. I get the best ideas there. Why is that?) If I'm constantly immersed in my own little writing world, then when I get that hour to sit down and really write, I spend less time warming up. The same is true if I write every day--it's easier to slip back into the story.
On the best days, I put in a CD playing music that relates to my story (currently: Loreena McKennitt's Nights at the Alhambra) and the kids and I dance, sing, and play around the house listening to it.* Then, whenever I can escape and not get distracted by blogs, facebook, and twitter, I write down what has been rolling around in my mind all day.
My husband doesn't know it yet, but I'm escaping the house shortly after dinner to slip into my other world and pound a bit on my keyboard.
* No, the baby doesn't sing and dance yet, but he is just about to start rolling all over the place. I'd rather he'd just stay put and warble.