1) Prep the seafood. If the seafood has skin on it, cut it off.
2) Dice up the seafood into small cubes. I recommend about 1/4-1/8 inch cubes.
3) Add juices to a bowl with the seafood. The liquid should just cover the seafood.
4) Chop all your additional ingredients (garlic, jalapeno, onion, cilantro, ginger, tomatoes, etc).
5) Add it all to citrus and seafood mix (leaving out the avocado and mango).
6) Add a pinch of salt and pepper at this point. Be sure to adjust for salt and pepper at the end too.
7) Let the ceviche sit for at least 30 minutes but an hour or two would be a good idea.
8) Drain out most of the citrus.
9) Add the chopped avocado and mango and mix it all up!
10) Serve with very thin baguette (toasted lightly for 5 minutes or so) or tortilla chips.