biggest mistakes in horror movies
 

the biggest one, assuming that the first bullet killed the bad guy and not making sure he/she/is dead.
Talking to (and trusting) a clown who lives in the sewer - IT
Picking up a hitchhiker - Texas Chainsaw Massacre
Trying to save the infected little girl - Carriers

just abit of fun :D

here is another one.

man/woman, standing there watching the killer kill your friend, when they could have had a good head start to run away.

Burying Church the cat into the MicMac burial ground in "Pet Semetary".

Look at the other way - try explaining to the police why you shot the guy who broke into your house 6 times then cut off his head and set him on fire...

haha, i think they may not believe that