When it appears that you have killed the monster, never check to see if it's really dead. It isn't.
If you find that your house is built upon or near a cemetery, was once a church that was used for black masses, had previous inhabitants who went mad or committed suicide or died in some horrible fashion, or had inhabitants who performed satanic practices there, move immediately.
Never read a book of demon summoning aloud, even as a joke.
Do not search the basement, especially if the power has just gone out.
If your children speak to you in Latin or any other language which they should not know, or if they speak to you using a voice other than their own, shoot them immediately. It will save you a lot of grief in the long run. NOTE: It may take Holy Water and several rounds of silver bullets, so be prepared.
When you have the benefit of a group of people, NEVER pair off and go it alone.
As a general rule, don't solve puzzles that open portals to hell.
If you're searching for something that caused a noise and find out that "it's just the cat," leave the premises immediately, if you value your life.
If you find a town that looks deserted, it's probably for a reason. Take the hint and leave NOW!
Don't fool with recombinant DNA technology unless you're sure you know what you are doing. Even then, don't do it.
If you're running from the monster, expect to trip or fall down at least twice, more if you are of a female. Even though you may be faster than the monster, you can be sure that it WILL catch you.
If your friends suddenly begin to exhibit uncharacteristic behavior such as hissing, fascination for blood, glowing eyes, increasing hairiness, and so on, get far away from them, as fast as possible.
It's best to just stay away from certain geographical locations, some of which are listed here: Amityville, Elm Street, Transylvania, Meskatonic University, Camp Crystal Lake, Haddonfield, Illinois, any desert town with one gas station, and especially Derry, Maine.
If your car runs out of gas at night, do not go to any nearby boarded-up, deserted-looking houses to phone for help.
Beware of strangers potentially bearing dangerous tools such as chainsaws, staple guns, hedge trimmers, electric carving knives, combines, lawnmowers, butane torches, soldering irons, or band saws. This is especially true if they are wearing a hockey mask or one made of human skin - often a dead give-away.