How do you get all three starter Pokemon in blue version?

my mate did it like this i managed to get squirtle and bulbasaur this also works on silver

You start the game(save when you get out the house) you get your first Pokemon right off pro oak you then do his little task thing cant remember what it is anyway the very first time you can, catch any Pokemon catch one suppose pigey store the Pokemon you got from oak then change to the next box

switch off (as fast as you can as the saving takes only about 1 or 2 seconds)

you begin again when you first leave your house then pick the other Pokemon you want from oak then do the little task thing then catch a Pokemon again check your Pokemon box there will hopefully be all the Pokemon you had and have .