Here is a short example of a few effects which can be used at low cost for any scream or horror type movie.
Making your own video or short movie or longform movie is now very possible for the average fan of gore or schlock. If you want to make a high class epic it will be harder but still possible. The key is to have software for video editing and a camcorder or video camera of some sort... and some friends. There are many things you will be able to accomplish alone.
Even Windows Movie Maker, which comes bundled free with most PC computers, will do a fade effect, The fade is basically mixing two images and brightening or dimming the lighting for one image as you mix the two together. Most low cost video editors do a very excellent fade and some do many different types of fades. The fade can be used to make a ghost or invisible man or you can make objects seem to appear on tables or on the road in front of a car.
A more complex fade can be used to give an effect like the beaming up of astronauts in the space movies. To do that you need to capture one frame of the video and use a photo processor like Paint, to color the person or object being beamed or teleported. Color that person or object with a chroma key color such as green or blue and then use that single frame to make a mask or overlay of a moving color background, sometimes called Visuals. Crop that video and overlay it onto your character in the video editor and fade it in or fade it out for the effect.
Scream movies rely heavily on special effects. They are sometimes called FX and some of the more expensive versions are called CGI. I recommend learning how to do low budget special effects like I show in my tutorials at YouTube. Most of the fun sci-fi movies had low budget effects. You actually can do better special effects with home computers now than a Hollywood producer could do twenty or thirty years ago. A good video editor can be bought for $50 to $200.
The use of still pictures with video pictures placed into the picture has been done for many years. In my video above I show how to put a small video picture into a photograph of an outdoor scene. To make it more realistic I have added some green screen clips that are overlays of the picture and video. As the dinosaur raises up in the video above you will notice there is a rock formation between the viewer and the dinosaur. That is just a still image of rocks with a green background placed over the picture and video content. There are about four layers of video and still pictures in that video. Be sure to get a video editor which has many tracks of video and audio and effects available. Sony Vegas and magix pro 14 are both good choices.
I did not add any music or sound to the above video. I do recommend learning to create music for your project. A minor chord that would suddenly be heard as the dinosaur appears would enhance the scene greatly.
When you make a gore or slasher movie or video, do not be afraid to use still pitures of mountains from which your actor jumps or over which the automobile crashes. You can have a scene like my video above with a UFO hovering overhead. Explosions are easy to do. Check Detonation Films website. They have some free effects.
Find your cast on Craigslist or in your school. You do not have to pay the actors if they are going to get credits and a copy of the video, or maybe several copies of the video. A low budget film will most likely be an expense and you will not see a profit. Make the movie now and learn more for the next movie.
Get a good editor and computer and learn to use the software. View my tutorials at YouTube and many other tutorials about how to make a sci-fi or zombie or UFO movie. Each video tutorial will bring you closer to understanding how to make your movie look professional.
Your actors will want to know what they are supposed to do. You know what the image will be. Do not be afraid to say "Louder" or "Don't smile" or "Don't look at the camera." Be in command. It helps the actor.
When you are choosing pictures for mixing with your video be sure to choos royalty free or original photos.
Work closely with the editor.
The best advice I can give you on casting is to find someone who is actually interested in the project. You do not need a "star" or prima donna. You will want someone who doesn't mind making a pot of coffee or maybe helping you present the movie after it is made. The actor with personality is way ahead of someone who has nothing but talent to offer.
Your movie title needs only to be great.
Most of your locations will probably be in your garage or basement or living room. If so, make it work. There is always a way to "cheat." Shoot day for night scenes or have a green wall handy for inserting green screen backdrops.