Regardless of whether you're riding a classic wooden toboggan or an inexpensive plastic model, a perfectly smooth bottom surface is the key to making it go fast. Start by using a soft rag to remove any debris from the bottom of the toboggan, and tighten any bottom-facing hardware to offer as much clearance over the snow as possible. If the result still isn't fast enough for you, you can add a coat of glide wax just like you'd use for cross-country skis.
Waxing a Toboggan
Liquid glide wax, which you apply directly to the bottom of your toboggan with a sponge applicator just as you would with cross-country skis, is by far the easiest and quickest way to wax your toboggan. Let the wax dry, then buff with a soft brush to make it even smoother and faster. This fix is relatively short-lived, but that's a good thing if you find the waxed-up toboggan is too fast for you.
For a longer-lasting solution, apply a solid glide wax -- not grip wax -- just as you would with with actual skis. Turn the toboggan upside-down, hold a warm iron near the wax block so it dribbles onto the toboggan's rails, then spread the wax evenly on the rails with a waxing cork or brush. Buff the wax smooth once it's dry.
Household Alternatives
If you don't already have ski wax laying around, you can use some household products to make your toboggan go faster. Spray WD-40, furniture polish or non-stick cooking spray on the rails of the toboggan for a temporary speed boost.