The good news is that as long as the fish is fresh you are fine. Let your nose be your guide. If you smell a strong fish odor that s a bad sign. Fresh fish should have a mild aroma. I ve eaten at sushi bars all over the world and have never gotten sick.
Most sushi bars are very sanitary and get the freshest fish possible.
Wasabi is the green condiment on your sushi dish next to the ginger. Usually the green stuff is actually horseradish as opposed to real wasabi which is a rare vegetable used as a spice primarily for seafood. Fresh wasabi is more expensive than the tuna your putting it on. Your other sushi companions include ginger slices which are for cleansing the palate between sushi dishes and the soy sauce which is for dipping. Low sodium soy is available usually in a green container.