Almost any kind of fish can be used to make sushi from. The most important parameter while choosing a fish to make sushi from, is how fresh the fish is. Ask at your local store when do they get the fish supply and buy it then. Other than that, and it goes for any kind of fish, whether it's for sushi or not, make sure you buy it from a clean place. look for "unpleasant odours", and the typical smell of fish, if there are any- Don't buy there! 

Cutting the fish- My rule of thumb is to cut the fish strips about a finger width, and the length should fit the seaweed sheet of course.