Newspapers and magazines, radio and television companies, receive a vast quantity of material every day of the year. It comes in many different forms. These include announcements from companies, government departments, research institutes and other bodies; material from national and international news agencies (Reuters, for example); and releases from public relations firms representing their clients' interests. The lay media also gain ideas from specialised publications . Sheer pressure on space and broadcasting time means that journalists can use only a tiny proportion of the information they receive through these various channels. How, then, do they choose what to cover?

Journalists and their 'gate-keepers' are receptive to novelty. Significant developments in science and technology for example, major advances in the treatment of a particular disease provide many examples of such novelty. As well as developments with concrete applications now or in the future, the media report discoveries that are simply inherently interesting. So while much "normal research" goes unreported, developments with practical implications for, say, medicine or agriculture will attract journalistic attention. The same is true of discoveries that are counter-intuitive or have an element of the unexpected.

The general media also feed off each other to a surprising degree, and they work to unwritten menus of topics that appeal to them at any one time. Stories about environmental pollution, for example, may be keenly sought this year but may be less popular with journalists and their editors next year. In engaging the interest of the media, it is helpful to be aware of what subjects are currently favoured on their agenda. Some of the most skillful initiatives in "placing" stories in the media are taken by people who see opportunities for providing new angles on stories that are already running strongly.

There is fierce competition within the media. Newspapers, for example, compete for readers and for advertising revenue. Nevertheless, their science correspondents often work closely together, attending many of the same conferences and discussing what they are planning to report. Many journalists also have an appetite for occasional "exclusive" stories which, if they are considered to be sufficiently important, their competitors will then have to follow up.