Language of the writeup: use the Case Studies in the beginning of Sleuth chapters as well as language in the book as your guide.
Introduction
Clear statement of research question. KEEP THIS CONCISE.
Description of data. If observational, how was the data collected? What was the experimental design?
Exploratory analysis of data: Give relevant summary statistics giving center and spread of data. These can be reported in a simple table or in a few sentences. Produce relevant plots tailored to the question at hand. Provide unique features of the data that could have an impact on the analysis: outliers, shape of distribution, sample size issues. Again, keep this very concise. If you make a table or plot, refer to it in the text. For example, you can give a regression line plot and describe the data in the plot in the exploratory analysis section, and discuss the regression line in the same plot in the statistical analysis section. Clearly label all plots.
Statistical analysis. This section includes information on the statistical tests performed, and should be written in a form similar to the "Case Studies - Summary of Statistical Findings" section at the beginning of each chapter in Statistical Sleuth. You will summarize the results of a regression analysis. Be sure to perform all relevant diagnostic tests to confirm fit of the model, and discuss the results in a couple of sentences.
Summary of findings and scope of inference. To what extent does our data answer the question asked? Mention any sampling issues (independence or possible correlation of data, sample size issues) that could have an impact on the analysis. What are the limitations of the model you have selected? Is there any problem with using the normal simple linear regression model for the purpose intended? The "Scope of Inference" sections of the "Case Studies" should be of use here. Remember that recommending a larger sample size isn't always realistic; you will not always see perfect "textbook" datasets, and that this particular dataset may be all that is available to answer the question.