talk the man in the game corner on two island, then go to three island and find lostelle in the forest
two island, but after a little while.
You go back to the boat you went to One Island in from Vermilion
on two island a gye whants two small or 1 big one
4, 5, and 6 island
He Whent to The Rocket Hideout on Five Island.
There is one just south of Cerulean city, in this one you can only raise one of your pokemon. there is another on four island where you can raise two pokemon.
After getting the national dex you can find national Pokemon around one island, two island, three island, four island, five island, six island and seven island.
You can't give the day care man two pokemon, but there is a day care on one of the islands that raises 2 pokemon. I think its 4 island.
at the cave in mt. ember where there is two rocket guys waiting for you (mt. ember is above 1 island (need surf))
There are two islands that are very rare and secret in Pokemon Emerald. The Southern Island that holds Latis or Latios that can only be reached with a Infinity ticket. The Mirage Island can only be reach if the right circumstances are met in game. The game will generate a number once a day and if the last digits match that of the friendship level of your Pokemon will the island appear.
in pokemon emerald you can go to the two island next to the battle frontier
You have to beat the Elite Four at least once then talk to Celio (the guy in the Island's Pokemon Center) then go to Mt. Ember and learn the password and battle them.