Whole Crab, Crab Legs, Lobster
I'll tell you right now, I have suffered many a bloody finger at the hands of crab who I swear are still fighting for life postmortem. You have to respect something like that. There is absolutely no way to be dainty, clean, or proper when eating these items either. Add to that, for all the work you have to do to get at the meat, in relation to shell volume, there isn't actually that much especially when it comes to crab legs, save for Alaskan King Crabs. In order to master this beast you will need crab crackers, crab forks, and crab mallets. If you are new to the crab game, take your time because the struggle is real, but you'll eventually get the hang of it.
I'm not really a fan of the raw oyster, though I like a fried oyster, but there is an art form to eating one properly and getting the best bang for your buck.
There are so many crimes committed against sushi, beginning with the phrase: "supermarket sushi." If you're getting the stuff from there, and believing it to be and telling friends and family that you eat "real sushi," there may be no help for you, but if you are the type that goes to a proper sushi restaurant or goes to someone making a fresh batch for you at home, there are some ways for you to get the most flavor and enjoyment from the sushi and some proper etiquette and techniques to employ to eat it correctly.
*Bonus: how to use chopsticks
You have been absolutely wasting the majority of your chicken wings by trying to nibble furiously to get the meat off. There is a way to get 99% of the meat off the bones which means more food for you, less wasted food.
Don't just quietly suffer by only ever eating the from can artichoke hearts. Enjoy a nicely cooked artichoke in your favorite sauce.
Watermelon and Mangoes
Figuring out how to eat a watermelon or mangoes isn't actually hard at all. Lots of napkins, a big plate, chomp, chomp, but cutting it and getting nice slices that don't waste the flesh can be.