Being an avid horror movie buff, I would like to offer three quick tips that usually guarantees a good movie pick.
1.) Avoid new zombie flicks. Unless the movie is apart of the original "Night of the Living Dead" series, leave that new zombie flick unwatched. It seems everyone who is anyone makes a zombie flick, but they are never good. Bad plot, undeveloped characters, and tragic scenery seems to plague these movies. Bypass them.
2.) Psycho horror thrillers are usually promising. These sub genre movies make for a great scare, but you get suspense, drama, and a mystery all wrapped up in one. Most movies that fit in this genre try to give a storyline that has never been done or not done to their full potential. Many times they are unique. Some can let you down, but overall they are awesome.
3.) Read reviews. The best way to help you determine if a movie is worth a watch is to check out the reviews for it. Yeah, sometimes the reviews can be misleading, but they are worth a try. Many times the best reviewers are the ones who wrote the longest reviews. Those reviewers are usually giving you the real deal about the movie, as they are trying to give you every detail they can. Read those first.
So there you have it. Good movie hunting!