Ok lets start of with mew
to get mew you need to get the old sea map where you can get at a nintendo event wich the next one is in new york i think
latios that is your choice when you get home after you beat the elite 4 your mom will ask you red OR blue i sugeste you pick blue for latios because hes a guy and he atacks by more thats just my opinion

latias you need to get the eon ticket wich you get at a nintendo event

lugia and ho-oh are in the same cave but you need to get the mystic ticket wich you get at a nintendo event also then wonse you get it go to lilycove city and it will take you to navel rock cave im pretty shur

deoxys you need to get the arora ticket wich you also get at a nintendo event
and wonse you get it a boat will take you to birth ilands

jirachi you half to see every hoen region pokemon in your pokedex then you go to mossdeep city and go to the lauch station where they lauch rockets in to space

well thats it for now bye