5 Things Death Note Teaches Us 

Okay..... I will think first.

Don't pick up weird objects that fall from the sky when you can't figure out a plausible explanation of where they dropped from (it was obvious that it couldn't have dropped from the school rooftop as it is too far away) and even them you probably shouldn't touch them.

Don't send the FBI to do a job for the CIA.

Don't pass around weird objects and especially don't let a murder suspect touch the object.

Don't keep people who are related the a murder suspect on the investigation team and preferably don't keep those who would be too blinded for their respect for their father on the team.

Don't give up everything that makes you who you are for a jerk (goes for both Naomi Misora aka the badass princess in leather and Misa).