Frost the cupcakes as you would usually. A great tip is to plop about a tablespoon in the center and then hold the knife still, and turn the cupcake instead. That makes it finish a bit smoother on the top.
Snip off the end of the decorator icing tube and make a dot in the center and three circles surrounding it, like a bullseye.
Take the skewer or toothpick and drag straight lines out of the center dot. Repeat this for 5 or 6 straight lines coming out of the center dot, sort of like the spokes of a wheel.
Finish these adorable cupcakes with a spooky plastic spider on top!