The way I done the Islands was to do it each Island in order from One Island to Seven Island. When I was on that Island I would search it for possible new battles and every location on it before moving onto the next Island. This helped me complete the Islands without having to look at Guides for help. I just need to get all the Unown Letters now for storage on Pokemon Sapphire and then all of them again for storage on Pokemon Leaf Green. I'm trying to get all 386 Pokemon separate on Pokemon Sapphire and Pokemon Leaf Green because I'm thinking of quitting Pokemon gaming after these.