When it appears that you have killed the monster, never check to see if it's really dead.
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 necrophilia or satanic practices in your house move away 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 which is other than their own, shoot them immediately. It will save you a lot of grief in the long run. NOTE: It will probably take several rounds to kill them, so be prepared.
When you have the benefit of numbers, never pair off and go it alone.
As a general rule, don't solve puzzles that open portals to Hell.
Never stand in, on, above, below, beside, or anywhere near a grave, tomb, crypt, mausoleum, or other house of the dead.
If you're searching for something which caused a noise and find out that it's just the cat, leave the room immediately if you value your life.
If appliances start operating by themselves, move out.
Do not take anything from the dead.
If you find a town which looks deserted, it's probably for a reason. Take the hint and stay away.
Don't fool with recombinant DNA technology unless you're sure you know what you are doing.
If you're running from the monster, expect to trip or fall down at least twice, more if you are of the female persuasion. Also note that, despite the fact that you are running and the monster is merely shambling along, it's still moving fast enough to catch up with you.
If your companions suddenly begin to exhibit uncharacteristic behavior such as hissing, fascination for blood, glowing eyes, increasing hairiness, and so on, get away from them as fast as possible.
Stay away from certain geographical locations, some of which are listed here: Amityville, Elm Street, Transylvania, Nilbog (God help you if you recognize this one), the Bermuda Triangle, or any small town in Maine.
If your car runs out of gas at night, do not go to the nearby deserted-looking house to phone for help.
Beware of strangers bearing tools such as chainsaws, staple guns, hedge trimmers, electric carving knives, combines, lawnmowers, butane torches, soldering irons, band saws, or any device made from deceased companions.
Listen closely to the soundtrack; and pay attention to the audience, since they are usually far more intelligent than you could ever hope to be.