Bad idea: Fly with a vacuum cleaner.
Good idea: Crucio someone
Bad idea: Crucio yourself.
Good idea: Take a walk with Fang.
Bad idea: Take a walk with the giant squid.
Good idea: Offer a candy to Dumbledore.
Bad idea: offer a candy to Fluffy.
Good idea: Go study for your exams with Hermione
Bad idea: go study for your exams with Peeves.
On to the next 5 ideas