I already posted this question in the Leaf Green questions and answers..

First you must obtain data on sixty different Pokemon, go to professor oak's lab and talk to him, he will give you the national dex. Then you must go to one island an talk to cellio.he will ask you to get the ruby and the sapphire( he will also give you the rainbow pass). The ruby is located near mt. Ember.go to the base of mt ember, hang a right and you should see two rocket members. Go to them and they should start talking. After they finish go to them,and battle them, they will leave. Now go inside the cave, at the end of it you will find a ruby. After taking it back to cellio you must go to six island. Hang a right from the pokecenter, go to the water and head down. You will end up in a large area full of grass and ledges (and a few trainers). Work your way to the middle, there should be a small white building with braille on the door(the letters say:CUT) go inside ,go straght up and you will find a hole in the floor, and like a drunken retard, you should fall in it. You will end up in a room with four holes and a stone with braille , this one says UP. The next one says DOWN, then LEFT then RIGHT. You will end up in a small room with the sapphire in the middle. When you go to pick it up a man will come down an steal it. Now you must go to five island, head right ,through the sorry excuse of a maze you will come to a building you must have heard both of the codes to get in. After a rediculously long maze of those paths used in the seventh gym(the one with the twins.), you will find a rocket, fight her and she will reverse one of the pads on the floor so you can get out heal your Pokemon and whatever else you have to do and come back with ease. Now go up, there will be a rocket, fight him, continue upward and you will find the jerk that stole the sapphire. Fight him and he will give it to you. Take it back to cellio and he will put it in the machine. And viola! You are now able to trade with ruby and saphhire!!!! (now don't forget to save, you don't want to have to do this all over again.)

P.S.:if you didnt know this already, this can only be done in leaf green and fire red.

Well on the frist island once you've given celio the ruby and sapphire ether cot to the machine and press a then you can trade or upstairsI forget which one(1 island only)