Writing proposals and job applications is arguably one of the most important tasks in the career of a scientist. The proposed ideas must be scientifically compelling, but how a proposal is planned, written and presented can make an enormous difference. This Perspective is the third in a series aimed at training the writing skills of professional astronomers. In the first two papers, we concentrated on the writing of papers; here we concentrate on how proposals and job applications can be optimally written and presented. We discuss how to select where to propose or apply and how to optimize your writing, and add notes on the potential use of artificial intelligence tools. This guide is aimed primarily at more junior researchers, but we hope that our observations and suggestions may also be helpful for more experienced applicants, as well as for reviewers and funding agencies.