Many seeds germinate better, and cuttings root faster, when they have bottom heat. Gardeners used to balance six-packs of seeds on top of the water heater or place seed flats on top of the refrigerator, but this space is often already claimed or impractical, and modern refrigerators are not warm on top. A seedling heat mat, available at garden shops or on line, is the easiest way to provide bottom heat. The 10- by 20-inch mats are the same size as a seed flat. You won't need it for a few weeks, but buy one now to help you through the winter.
Brent Heath, of Brent and Becky's Bulbs, taught me an off-season use for a seedling heat mat under a desk. The gentle, low-voltage heat keeps your feet toasty while you're working (Dan demonstrates this, above). You have to remember to keep your feet on the mat, of course, and if you have a cat, you'll lose your place if you move your feet for long.