You must catch at least 50 kind of Pokemon. Then go and speak to Prof. Oak, he will send an aide to give it to you.
Then go to one of those houses between the cities, and talk to the Aide upstairs. He will give it to you.
Good Luck ^^
After you catch 50 Pokemon, have Prof. Oak look at your pokedex. He will send an aid with the Exp. Share
An oak aide in a big building east of fuchsia city has exp share you need to record 50 Pokemon in your pokedex and show him that, he gives you exp share for your accomplishment.
one of Prof. Oak's aide's
call me at 870 949 1949
Route 14/15 guard house upstairs
no, except you get one from your friend or use some gameshark code
Just have a friend with leafgreen, firered, ruby, sapphire or emerald trade you a Pokemon holding the exp share they got.
An oak aide in a big building east from fuchsia city has exp share.
well if you have a exp. share use it on weak Pokemon and on a x-tream strong Pokemon and get big levels
give the exp share to a weak Pokemon when you use any Pokemon to fight exp goes to the fighting Pokemon and the 1 with the exp share.
Once you capture 50 different Pokemon or own 50 different Pokemon you can go east of fuchsia city and go inside the big building and go upstairs and talk to the scientist say YES to his question to get exp share.
First capture or own 50 different Pokemon, Second go east of fuchsia city and go in the big building go upstairs and speak to the oak aide show him you caught or have owned 50 different Pokemon to receive an Exp Share.