Wash rice until water runs clear. Soak 1-2 hours. (If using wholegrain rice, soak overnight.) Drain and put in pan with equal volume cold water. Bring to boil, cover and simmer until all water is absorbed, 8-10 minutes.
Blend well together rice vinegar, sugar and salt. Tip cooked rice into large shallow dish and sprinkle over the rice vinegar mixture. Mix together carefully and allow to cool. (Some people suggest a hair dryer to speed things along!)
Prepare fillings as desired. For example, chop veg or tofu into long thin strips, shred and wilt greens, dress shredded cabbage with rice vinegar and salt, and maybe toast the seeds.
Lay out your bamboo mat, wax paper, or (especially if doing inside-out rolls) mat covered in wax paper/cling film. Place nori shiny side down in 'landscape' orientation at the bottom of the mat. With wet fingers to stop it sticking, scoop around 1/2 cup of rice. Spread over nori so it's around 1/4" thick, with 1/2" clear at the top.
For inside-out rolls: Sprinkle 1 cm sesame seeds over the rice, then flip. For normal rolls, skip this step!
Fill your rolls: Line fillings along the bottom third. Ideally lay fillings next to each other in stripes rather than piling high. If you need to layer, put the biggest ones underneath and smaller things on top.
Roll from the bottom up. Dampen the final edge slightly to help it stick. Squeeze and roll back and forth a couple times at the end to secure everything. Chop with a sharp knife, sprinkle with seeds or chilli mayo or any other toppings.
Serve with soy sauce, wasabi or any other sauces you like, and pickled ginger if you have any.