Title your lab. Sometimes the title will be assigned by the teacher, other times you will be asked to come up with your own. The title should briefly summarize the focus of the lab: for example, "The Rate of Osmosis through Semi-Permeable Membranes."
Compose your introduction. The first section of your lab report is called the "Introduction" or "Purpose." This section states what your experiment will attempt to do and how you expect it to turn out. State the theory or hypothesis that you are attempting to test, and add information about previous scientific studies or experiments that are relevant to your theory.
List your materials in the "Materials" section.
Explain your "Procedure." This section is a step-by-step explanation of your experiment as you carry it out. Write the steps in order, unnumbered, as a paragraph, without frivolous narrative. Include any variables and controls. Also add any safety information in this section, and any sketches or diagrams of your method.
Write your "Results." List the data that you collect, in narrative paragraphs or tables, or whatever format works for your particular experiment.
Make an "Analysis" of your information. This section is where you describe what happened during the experiment and whether the results turned out as you expected. Even mistakes or undefined results should be listed here - presume that everything that happened is relevant, and propose theories for unexpected results. Solve any equations brought up in the experiment. Explain any problems or complications that prohibited an action from occurring. Include graphs here. Also, inform the reader of estimations you made to come to your results and why you made those estimations.
Write your conclusion. In this section of your lab, you talk about the significance of your results. Your Introduction stated a theory. You used the experiment to test that theory. If the theory was disproven, discuss whatever information you learned from the experiment. Apply your experiment to real life by discussing an issue or problem relevant to your findings.