I made sushi this weekend for the first time in several years. It is actually very easy if you have access to the right ingredients, and I should do it more often. For the filling, I stuck to something I could get easily in my local supermarket but there are many other possibilities such as minced crab sticks and avocado, strips of omlette and pickled radish. I made the traditional rolls as pictured above, and the inside out rolls as pictured below:

You will need a bamboo rolling mat which can be bought at Asian stores and larger supermarkets.
Ingredients for simple California rolls - makes three rolls
1 large mug of white rice
water
1 dessertspoonful of rice vinegar or rice wine
half a teaspoon salt
1 teaspoon sugar
3 sheets of roasted seaweed lava
160g can tuna
a good dollop of mayonnaise
half a cucumber peeled and cut into 9 strips
Toasted sesame seeds to sprinkle
Cook the rice by the absorbtion method, either follow the instructions on the pack or cover the rice with your thumb's depth of water and cook over a low heat until tender and all water is absorbed. Leave to cool.
Mix the vinegar, salt and sugar until all dissolved then drizzle over the cooled rice and fork through. This will make the rice sticky and glossy.
Drain the tuna and mash up with some mayonnaise.
Lay a sheet of seaweed on a bamboo rolling mat, lengthwise and rough side up. Spread some rice over the the sheet but leave a 1.5cm strip across the top. Don't spread the rice too thickly. Spoon a stripe of tuna horizontally about 2 cm from the bottom from end to end. Then above the tuna, lay 3 strips of cucumber end to end.
Start rolling the mat from the bottom. Do one roll over the filling and squeeze firmly. Then lift the edge of the mat slightly and continue rolling. Wet your finger and wet the top edge of the seaweed before the final roll. This will seal it.
Use a sharp knife to slice the roll, you may need to wet or oil it between slices to stop the rice sticking.
For inside out rolls: Spread the rice over the seaweed but do not leave a gap at the top. Flip over so the rice is now on the bamboo mat and the shiny side of the seaweed is facing upwards. Place the filling on the roll as normal and then roll up. Sprinkle sesame seeds on the rice.