There are many types of horror movies out there. Some that will scare you some that are more into the blood and guts and then you also have your mind benders and suspense horror movies. Sometimes it could be hard to figure out what kind of horror flick your wanting to watch now and it also depends on the situation, for example if your on a first date you might not necessarily want to watch a movie filled with blood and guts.
The best kind of horror movie for a first date would have to be the scary type of horror movies. But right there we seem to run into a problem as well don't we? What makes a horror movie scary? First off you have to find out what scares someone. Some people may not take a creature movie the same as a serial killer one or a ghost or vampire one. I tend to find that the most realistic situations seem to scare people the most. If there's some possibility that it could actually happen it always raises the fear factor, so if you're looking for a real scare your creature features may not necessarily be your best choice to frighten your friend or date.
The best kind of horror movies to watch with a group of friends would probably have to be the mind bending or suspenseful movies. Your going to want something that's going to keep you on the edge of your seat and keep you guessing what's going to happen next and guessing who the killer's going to turn out to be. It keeps everyone interested in the movie and gives you and your friends something to discuss after the movie.
If you're wanting to gross out your friends though you could always go with the blood and guts hack and slash them up horror flick. These are relatively easy to find although you have to be careful about the cheesy ones. Some of these type of flicks are usually poorly written with terrible acting.
My last piece of advice will be to always check your reviews and ratings. You don't want to make a first date awkward by bringing nudity into the picture. The reviews will also let you know the opinions from other people to try to decide whether the movie will be worth watching or not.