The easiest way to beat the game is to start from Area 1 and go through Area 4 until you get to King Boo, and then, you suck him up with that ultra awesome vacuum cleaning device that the good ol' Professor Elvin Gadd gave to you. Help the elderly, its good to do! That's how you win.
Now to be serious, if you really want some help, go to IGN and look through Walkthroughs submitted, by not the official one with an image given in the site, because you must register to get it.
Find Mario and finish the final boss, you can shoot the spiny balls back at bowser to make king boo pop out, it's vaccumming time.
in the twins room once you beat the twins.
in the basment
walmart
trapped in a portrait on the final level of luigis mansion
Yes there will be a luigis mansion 2. Its called the elictric boogaloo
probably in the laundry room
unfortunatly, you have to beat the game 15 times. then go to options menu and choose god mode.
Suck up a Shadow Ghost until it becomes a ball and shoot it at the real ghost then you can suck it up!
you dont get luigi mansion in the day
Go to VidoEmo.com. there are plenty walkthroughs there.
poltergust 3000
no luigis mansion is on gamecube buy 1 they r cheap 30 $ or so