I don't watch a huge amount of horror movies but I used to! Here's what I gleamed from my experiences of watching 90s & 00s horror flicks. Feel free to add you own insights.
  1. If you have sex, you die. (Pre-Scream 1996)
    This is a classic way to figure out who dies in horror movies before 1996. Scream inverted and mocked this trope so it's less reliable but if a hot actor is there specifically to just have sex with a more major character, they are most likely on the chopping block even nowadays.
  2. If the character decides to investigate the loud sound heard at outside the bedroom door/in the basement/outside.
    Come on folks! This is the classic horror scenario. Especially when it's been established earlier that there's a serial killer on the loose already. You KNOW things aren't going to end well. Under NO circumstance should you go check on that sound. Lock your door & call the police!
  3. Corollary rule: if the character is super curious in any way, they are probably going to die.
    The guy who goes to investigate the sound? Dead (see above). The nerdy guy who tries to hack into the computer mainframe to see if there really is a conspiracy? Totally dead. The gal who is freaked out about the sounds but then puts her ear up against the door when the sounds stop? So dead (probably by an axe or sword stuck through that door - don't put your ear up against a door or wall folks.)
  4. In a group of friends, the "new" guy/gal is going to die first.
    Someone brings along a person they are dating and introduces them to group for the first time? That person is SO dead If there's an attack by zombies or rabid dogs. It just how it works.
  5. If everyone is old friends in the group, the funny or ethnic person dies first.
    The white person always survives. It's the sassy black girl or the funny homosexual sidekick that gets killed off. The funnier or sassier they are, the longer they survive though. So if you are a person of color you better be fucking funny or sarcastic as all hell.
  6. If the character is a "type" most likely they will die.
    Nerd. Jock. Cheerleader. Sassy sidekick. Fat girl. Fat guy. Hacker. Popular kid. Loser. Whatever. If the character is strictly a stereotype, they're not going to survive.
  7. If you're an asshole you die.
    Unsympathetic characters die first. The jock that knocks the books out of the nerd's hand in the hallway and then laughs? Dead. The bitchy girl who says horrible things about the new girl in the JC Penney's outfit? Dead. Moral of the story: don't be an asshole.
  8. Figure out who the lead of the movie is. If this person survives the first scene or the first act they are (usually) in it for the long haul.
    This isn't necessarily the biggest name actor. Sometimes the big name gets killed first. But usually the big name dies in the first scene in a spectacular way. Examples of leads and big actors that died in the first act are Drew Barrymore in Scream and Janet Leigh in Psycho. If they last past the 1st act, they'll liable to last until the end though.
  9. Finally, if there is a sequel, look at the movie posters. The people who make it to the sequel survived. The ones that didn't died.
    This only works for high profile sequel. Direct to video doesn't count because they are low budget and often can't get the same cast. But I once rented I Know What You Did Last Summer and I Still Know What You Did Last Summer at the same time. I knew exactly who died just by the cover alone.
  10. Of all the "types," Stoner is the most absolutely certain to die (and quick!).
    Suggested by @angusisley