How do you rescue luigi?

you don't

There's no such thing as Luigi in Super Mario 64

First go to Big Boo's haunt. In the mansion, triple jump up to the second floor. Go in the far right door. Get the power flower. Bounce up to the 3rd platform. Go in the door and jump into the...

you can look at the left or right of a level after you save luigi to play as luigi

kill the big boo in the backyard of the castle(mario needed), to go to boo's mansion,go in the front door,go to the 2nd floor(if you have not gotten go on a ghost hunt just triple jump up),go in the...