Make a hypothesis if you want to prove something. Or come up with a list of things you want to know about Venus flytraps, such as how they decrease disease rates at locations where flying insects carry malaria.
Research, depending on the depth of your work. If you are writing an academic paper, read about flytraps in your library and online. If you are writing something more in-depth, consider buying some Venus flytraps and observing them in your specific environment. You're looking for facts that support your hypothesis, or that are relevant to the list you made.
Write an outline. State your point in a thesis. List the supporting details -- your proof or basic list of facts -- and end with a conclusion. Don't worry too much about outlining your conclusion.
Write an introduction, starting with a brief description of the flytrap: its functions, climate, location, prey and cultivars, for example. End with a thesis sentence that includes an opinion -- in this case, what you wanted to know about or prove. Include basic references to what might come up in your writing, in the order of appearance. Your introduction should be a map for your readers.
Write out your facts. If you are writing a book, you should break these facts up into chapters. Treat each chapter as another essay, and repeat the whole process of writing for each chapter. Include an introduction, a list of facts and a conclusion that ties your facts to your thesis and states how it proves your point. If you are writing about Venus flytraps in general, state how the listed fact might matter to the reader. If you are writing an essay, start each sentence with a brief overview of the fact, then go into detail, following the claim-data-warrant format. The claim is the statement of opinion. The data are the facts that support this opinion. The warrant explains why the facts support the opinion. Some ideas for this part of the paper include descriptions of flytraps' physical state, behaviors, required climate, mechanisms, digestion systems, and information from the International Carnivorous Plant Society.
Write a conclusion. In general, conclusions should tell the reader why things matter. The conclusion should tie off all loose ends and summarize the significance of the plant, as well as tie all the facts back to support the claim you made in the introduction.
Go back and read over your piece of writing. Repeat until you think it's flawless. It probably won't be; ask at least one or two people for editing help, or at least critical reads.