What kind? Trout and salmon.
How? In a smoker
It's been a while, since leaving PA I don't fish very much, but I used to smoke just about all of the trout I caught. And Walmart used to have whole salmon for pretty cheap, so I'd smoke those when they had them.
I used a basic brine of water, salt, sugar, and apple juice. Leave them in the brine for 12-24 hours before smoking. The trout I smoked hole, but the salmon I filleted, leaving the skin on.
I prefer fruit tree wood for smoking fish. Apple, cherry, or pear were my favorites.
Thinking back, I've also used beer or wine, in place of apple juice, in the brine. Didn't typically add many spices, sometimes garlic powder, and sometimes a little lemon or orange juice/pieces.