voici un petit texte (en anglais) duquel je me suis inspirée pour mon entrainement :)
Citation:The number one hint or tip is this: rolling sushi is a self-correcting process. If your first roll does not turn out quite right, eat it to hide the evidence and roll another, which will be much better. If it has been a while since you made a roll, the first one may leave something to be desired, but it will all come back to you, like riding a bicycle or playing a piano (if you knew how to do those activities in the first place).
Rice doesn't stick to nori, or roll does not stick together when rolled. You most likely did not use enough vinegar in your rice. The rice should be very sticky, annoyingly so.
Roll is too thick, or does not hold together well. You probably used too much rice, or packed it down too tightly. The rice should be spread on the nori to within about 5/8-inch of what will be the outer edge, should not be squished onto the nori, and should not cover the nori completely. You should be able to see nori between the rice kernals, perhaps 1/4 to 1/3 of the space should be open to the nori below the rice.
Cucumber can be cut into larger chunks which are easier to work with. Try quartering the cuke lengthwise, removing the seeds, then cutting the flesh into a few large pieces about 1/4-inch thick by 3/8- inch wide. The length of the pieces should be half the width of the nori.
The thick-skinned black avocadoes are easier to work with. Cut in half and remove the pit. Then cut each half into half again. Using a paring knife, slice the avocado in the peel, then run the knife just under the peel to cut the slices from the peel. It is easier and faster than peeling the avocado and then slicing it.
Place a square of plastic wrap on between the nori and the bamboo mat when making rolls. This will keep the rice and messy ingredients out of the mat and make it last longer. (Washing a bamboo mat is NOT recommended, it warps when it dries.) Peel the plastic wrap back with the mat as you roll. When you are finished, wrap the roll in the plastic wrap and put the roll in the refrigerator. When you are finished making several rolls and are ready to serve them, unwrap them and slice them.
voilou :)