Start by cutting a sheet of nori in half. Purists use a knife, amatures fold and tear the nori, I prefer to use scissors. I find that I get the cleanest cut and nicest edge on the nori using scissors.

Place your half sheet of nori on the rolling mat like this.

Moisten your hands with tezu and spread rice onto the nori using your hands. Leave about 1/2 an inch of the nori bare. Beginners may find it's easier to leave a bit more than that. Spread some wasabi along your rice.

Add your ingredient. Here I'm using left over pieces of tuna from sashimi I cut earlier that evening.

Holding the mat with both hands, carefully roll the bottom end over the filling, taking care to squeeze and compress evenly across the entire roll.

Here I've opened the rolling mat back up so you can see what I've done. If there's a bit too much rice at this point, you can use the back end of your knife to scrape a bit of it away.

Continue rolling the nori around the rice and ingredients until the bare nori seals itself. If it doesn't seal on its own, use a slight bit of tezu to seal the edge off.

If your knife is sharp enough, cut the roll in half now. If your knife isn't the greatest, put the roll in the refrigerator for a few minutes. This allows the roll to harden slightly to make it easier to cut. Once cut in half, place the pieces on top of each other as in the picture.

Continue to cut the roll into six pieces by cutting through both halves at once. It's bad luck to cut a roll into four pieces, and six is the standard amount.