A cheap medical style heating pad has worked well for me. While this is not a must have item, I have found that with many species this can literally half the time required for germination, and it can boosts the germination rate greatly. They had much larger ones for about twice as much, and if I purchase another, I'll get a bigger one. Keep in mind, using a heating pad this way will most certainly void any manufacturer's guarantee. Well for those of you out there on a shoestring budget, there are a few things you can do with practically no cash at all.
Seeds require moisture and oxygen to germinate, with no exceptions.
Plastic sandwich bags, made of polyethylene, permit transfer of oxygen, but not water. This has several advantages over simply placing seeds in soil. The first is that water loss is greatly reduced. This means that the seeds are not constantly being cooled by evaporation. If your room temperature is 70, moist soil in that room may be as cool as 65.