Read published abduction stories as research before writing an alien abduction story. Watch interviews with individuals who claim to have been abducted. Create a believable abductee by giving your character the attributes of a real abductee.
Imbue your story with a sense of disorientation and wrongness. Create abductees that are unwilling and horrified by the alien abduction experience. Remove self-control from the actions of the abductee. Give all control of human physical motion to the aliens.
Allow only telepathic communication between aliens and abductees. Developing an alien language immediately tips others off that your account is not credible. Detailing an alien ship is acceptable.
Describe alien abductors as small gray creatures with pointed chins, large eyes and only holes for a nose. Include a taller alien if you want to write about medical experiments.
Detail extensive physical exams performed by the aliens on their human abductees. Describe medical procedures that are invasive in nature and leave marks on the body. Give your abductee unexplained scars and marks to enhance the story.
Include time loss in your story. Detail how the abductee returns to the abduction site having no memory of how long they were gone and what occurred. Write of a traumatic event or therapy that brings repressed, credible memories to the surface.
Set your story in a time or place that has reported UFOs or odd celestial events. Combine reality and fiction to create the most credible alien abduction story.