The ability to write is an essential component of research. We write to communicate with readers. Our readers include funding bodies, thesis examiners, manuscript editors, reviewers, or readers of a journal. In each case, we write to convince a reader of our argument. In reports, we also write to allow a reader to check and interpret our findings for themselves. Good writing conveys information to readers as clearly and simply as possible. Poor writing obscures meaning, frustrates the audience and puts them off reading our work. Poorly crafted writing can make the reader suspect that our science may also be confused. To avoid this, write clearly, simply, precisely and concisely. Writing takes practice. In this chapter I cover general points, which apply to all scientific writing. I begin with advice on drafting, and the need to revise, obtain feedback and revise your draft again. This iterative process can come as a surprise to students accustomed to submitting work for a deadline, then forgetting about it. I then cover general style, followed by specific topics including structure and clarity.