Many sushi aficionados understand the routine of a chef and omakase, the chef’s choice. The idea of sequence at a sushi counter is key to understanding and enjoying the experience. The first fish to be served are shiromi, white fish and it is customary to begin there. A beer is served to warm up your palate and energize your taste receptors. Then the fish is served and typically you’ll have nigiri, (fish and rice) or sashimi, no rice. It all depends on part a clients budget, and the chefs opinion, and client: http://mesubim.com/2014/11/30/hirame-c-c-ponzu-engawa-video/ and such fish is served with classic ponzu.
The key to shiromi is the fish should be lean, clean and almost tasteless. I know it sounds odd, but very often the combination of a fish, vinegared rice, nikiri and wasabi is a refreshing taste, a neutral taste bound together by the complexity of the combination.