I also first start with maguro or otoro. If it's great then I either order uni or ikura. Uni is a great test to tell if the sushi-ya is good, but when it's bad it really is awful so I prefer to first see the quality of the tuna before ordering uni. One trick by the way for those who go to a kaiten-sushi in japan, usually the quality is of course not as good as a sushi-ya but some of the better ones are quite alright if you order directly all the sushis you want and don't take them from the automatic tray where they are not as fresh anymore...
