One easy recipe for ceviche uses 1 3/4 pounds of tilapia or other white fish, 1 3/4 pounds of shrimp or a combination of shrimp and fish. Another just uses shrimp.
Other ingredients are 2 tablespoons of green onions, both white and green parts chopped, 2 tablespoons of garlic, chopped, 2 peeled shallots, finely chopped, 2 seeded and chopped Roma tomatoes and 1 tablespoon of chopped cilantro leaf. The remaining ingredients are 1 1/2 tablespoons of hot sauce, 1/2 jalapeño pepper, finely chopped, 1 teaspoon of salt, 1/2 teaspoon of pepper and 1/2 cup fresh lime juice.
Combine everything in a large bowl, and mix thoroughly. Make sure that there's enough lime juice to cover all the ingredients. Cover the bowl, and refrigerate for at least two to three hours. When it's ready, the seafood should have an opaque "cooked" look. Stir before serving.
Another ceviche calls for 1 pound of shrimp, 1 cup of lime juice, 1 cup of seeded and chopped cucumber, 1 cup of seeded and finely chopped tomato and 1/2 cup chopped fresh cilantro. The other ingredients are 1/2 cup finely chopped red onion, 1 serrano chile, deveined, seeded and minced, and kosher salt to taste.
Put the shrimp in a bowl, and add 1/2 cup of lime juice. Let it "cook" for exactly 15 minutes. In the meantime, mix together the rest of the lime juice with the herbs and vegetables. Add these to the shrimp, and mix well.