It is hard to spell the name of this dish wrong. Virtually anything you can think of upon hearing the word will turn out to be the way it is spelled in some part of the world. The good thing is that it is even harder for the dish itself to go wrong.
You need three things, if you ask me: very fresh fish, citrus juice of some kind, and cilantro. The exact details don't matter.
To make this, just cube or slice the fish, put it in a glass container and cover it with the citrus juice. You probably want the fish to fit somewhat snuggly in the container. Put a lid on it (plastic wrap will do as well), and let it sit in the fridge. How long? It depends on your taste and the size of the chunks. I'd say between 30min and 1h. After that, just sprinkle chopped cilantro on top, and serve with boiled potatoes (or yucca) and fresh corn. You can also serve it with green plantain chips. Or serve it in a martini glass with chunks of avocados, if you want to play it fancy. The possibilities are endless.
For the record, here's my favorite way of making ceviche: I use whatever firm-flesh fish fits my budget at my favorite fish market (even tilapia works fine, though when my wallet can handle it I opt for red snapper), and I mix in some thinly sliced red onions and 1/4 of a teaspoon or so of diced habanero peppers, handled with utmost care. I marinate that with a combination of lime, lemon, orange and grapefruit juices. Before serving, I mix in some tiny cubes of bell peppers of different colors, and tons of chopped cilantro.
PS: No salt, no pepper. Believe me.