Develop a simple but cinematic story and script establishing the needed sense of danger for the main character and the other characters in the movie. Some of the popular elements a thriller story holds include suspense-filled chase scenes, "whodunnit" plotting that allows the audience to wonder who killed a character or who committed the crime in the story, shocking sounds and visuals that surprise the audience every now and then, and unexpected twists and turns in the story that provide adrenaline rush to both the characters and the audience. Usually, the plot of a thriller intends to isolate the protagonist from his or her surroundings (and possible help) as the danger to him or the things he holds dear grows.
Solidify the characters in your story in order to justify how they react to the many conflicts around them. This also helps in the logical and creative aspects of the movie where the characters' decisions become crucial to how the story progresses. You may wish to write a character breakdown describing short back stories and personalities of the characters. This becomes the primary basis for establishing the flow and pacing of the story, and may help the actors better immerse themselves in their characters' needs, goals, motivations and experiences.
Allow the camera to take on human qualities during the shoot by letting it roam around playfully in your various shots. Depending on the specific scene, camera movement or non-movement should generally evoke something suspicious in many scenes, as if the viewers of the movie would feel like they are actually involved in uncovering the mystery in the story. This way, you can also play with the audience's mind and emotions.
Usually, thrillers use the point-of-view shot where the camera works like the eyes of the character. This allows the audience to share the same view of the scenes the way the character sees it. If the character suddenly looks up or turns his or her head towards the other direction, the camera imitates such movements in a point-of-view shot. Evoking something suspicious can also be utilized by designing the scene with props that can serve as clues to solve a crime or mystery. Lighting the scene in a puzzling, strange or curious way provides a more atmospheric mood to further evoke the thrill needed in the movie's various scenes.
Put emphasis on the pacing of the movie during editing. Use variations of tight and long shots, short and long takes and moving and stationary shots to visually provide an effective succession of images, emotions and ideas.
Simple cuts can simply be spliced together for scenes that evoke the feeling of suspicion. You can play around with shots of the characters' faces to emphasize their feelings and intercut this with their point-of-view shots and other insert shots that suggest clues about impending danger or anything they are looking for. You can put transition and other visual effects in the scenes during editing to further establish a physical, emotional or even supernatural quandary.
Use sound, music and silence to evoke the needed emotions in every scene. Creatively infusing these elements in accordance to the visuals shown on the screen creates the needed thrilling mood and atmosphere for a thriller movie. Generally, a loud bang after a long established silence with only the sound of footsteps heard creates a feeling of being restless, nervous, tensed or alarmed. From orchestra to single-instrument music, the tone, melody and beat of a musical score also contribute to the required emotional investments for a thriller movie.