A relatively easy and mess-free way to make basic filled rice balls (onigiri). I believe that traditional onigiri are made in triangular or ball shapes and are formed in the palms of your hands, then covered with a strip of nori. You can also find cute little molds to make bunny or cat shapes to make these tasty treats even more appealing to children of all ages. This technique uses a sheet of plastic wrap to help you form the rice balls without getting your hands too messy.
Update: I've received a lot of good comments about the traditional method of wetting your hands before working with the rice to keep it from sticking to your hands. The plastic wrap makes it easy for beginners to form the balls; once you're comfortable with that, you should definitely try the wet hands method for a more natural way of forming the rice balls.
Step 1: Lay out the ingredients
First you must make sticky rice. Use short-grained sushi rice and cook according to the directions. I like to add about 1/4 cup more water per cup of rice to make it stickier.
Place a couple tablespoons of the cooked rice in the center of the plastic wrap.
Place your desired fillings on top of the rice. In this example, I used common "Philly" roll ingredients: smoked salmon, cream cheese, and chopped chives (instead of scallions).