You must decide on what you desire to describe. The event can be an experience you had, or an experience of someone else had. The event may have occurred in the distant past or more recently or it may be ongoing in the present.
Characterize the type of story that you will tell. True stories can be narratives, biographies and autobiographies. Determine which type your true story will be so you'll know how to write it. For example, if the true story is a narrative or autobiography, you will write it in the first person. However, if the true story is a biography, you will write it in the third person.
Organize your information. Sort out your ideas in a logical form. Outline your information. Every true story has a beginning, middle and an end. On a separate piece of paper, make three separate headings that correspond to these categories. Then, under each of these headings, write information that corresponds to each section. For example, under the heading titled "Beginning," write facts that will contribute to the opening of the story. Under "Middle," write facts that elaborate on the ideas presented in the opening. Under "End," write facts that contribute to the concept of a resolution, or how the main event affected the person you are writing about.
Write the true story. As you're writing, use your outline to help you. True stories should have an informative tone. If you are writing a personal account, then the contribution of your personal reflections and opinions will provide a certain amount of passion or emotional depth to the work. However, if your true story is a biography, or a true story about another individual, do not put your opinions into the work. This will distract from the main objective of the story, which is to provide insight about someone else, not to portray how you felt about that person or her experience.
Proofread your work. Check over your work and make sure that you included all the necessary information. Also make sure the true story has proper order and is not stilted in sentence structure. Spelling, punctuation and grammar are always important elements to check.