The best ways to present science fair research are by creating a project journal and writing a research paper. A journal records your thoughts, questions and observations during the project. The research paper presents the findings and documents the steps taken to achieve the outcome with resources to support the process.
Create a journal using an empty notebook. Write informal entries in a conversational tone and take down information and observations. The first entry coincides with the first day of the project and continues through to the outcome of the project. Early on in the project, record the reason you chose the project over any other ideas. Consistently write entries throughout the project and detail as much of the process as possible to make it presentable during the science project fair or presentation.
The research paper is a formal document and follows a format selected by your instructor or school. Clearly write your hypothesis going into the project and each step taken to achieve the results. Document the materials, ingredients, resources and time period used in the course of the project. Use the scientific method as a foundation to explain observations, experiments and data collected. End the paper with the results and explain if they aligned with your hypothesis.