Good Sushi Nori should be dark green in color, and not black. Between uses, keep it stored in a zip-lock bag.
Moisture is sushi nori's worst enemy.
Keep the bag of dessicant that comes packed with the seaweed, and put it in the zip-lock bag. Allow about .5 inch of the bamboo mat to extend past the bottom. It makes it easier to grasp when you start rolling. It's sanitary,It will prevent stuff from sticking to it, and make clean-up easier. Wet your right hand in the vinegared water, scoop up a loose handfull of rice, and spread it from the center outwards, with your finger-tips.