After you have written your first (or seciond) draft, try to organize your ideas, to provide structure to your report. Here are a few tips on how to do that:
Mindmap: Creating a mindmap of your chosen topic can be helpful to get an idea of the relationships between the different parts of what you want to write about. This way, you can also cluster ideas together that belong together, and distinguish the main points from less important matters.
Outline: Developing an outline (a "skeleton" of your work) can help you structure your report. In an outline, you write for each section of your report (introduction, methods, results, etc.) what you want to discuss there in a few sentences or keywords. This provides guidance when writing.
Topic sentence summary: Find the topic sentences of each paragraph. The topic sentence contains the main idea of that paragraph. In theory, all the topic sentences together should provide a summary of your report. Does this yield a logical story? Does it contain unnecessary things or are you missing a step in your chain of logic? Does a different order make more sense perhaps?
If there are more core sentences in one paragraph, it is better to split it up to increase readability.
Read like a reader who does not know the topic: Make sure you write for people who have no knowledge of the topic you are focusing on in your research. This means that you have to explain your argument step by step, explain more and give examples, so that the reader can follow your reasoning.