Futurists are those who attempt to predict and analyze the future. There are professional futurists, who do futurism for a living, as well as amateur futurists, who look at the future in their particular area of interest. The arguments for modern futurism emerged in the mid-40s, pioneered by the German Ossip K. Flechtheim, who said that even if we can determine the most basic statistical trends and plot them a couple decades in advance, we'd be generating valuable information for society to use. Many large organizations now employ futurists and scenario planners, to help them get an edge on their competition.
The task of the futurist begins with looking at historical data, extracting regularities, and projecting those trends a bit, if only to see what numbers pop out. For example, the human population has doubled roughly every 34 years for the last hundred years or so, and while the rate of doubling has slowed down slightly in recent times, it makes sense to assume that the general trend will continue, if even the doubling time is extended to, say, every 40 years. General and uncontroversial statistical trends like these are the canvas on the futurist paints more speculative projections. Futurists must be careful about any wild assumptions in the basics, lest they incur the ire of those who pay them to make serious prognostications.
After putting together a general idea of the next 5, 10, or 20 years, a futurist will often engage in "scenario building" - formulating concrete scenarios and classifying them on the basis of their likelihood. For example, "probable," "possible," and "wild card" scenarios. These help the company or organization in question choose their actions cleverly in the present so as to give rise to the future of their choice. For example, one might say it is probable that we will do the majority of our shopping online in 20 years, but improbable that the majority of work will be conducted in virtual worlds.
Certain scientists tend to get excited about futurism. As science describes the world around us with more precision and empirical support than the guesses of most laypeople, scientists are frequently part-time futurists. Because many scientists work on tiny pieces of small problems, they like to sketch a look at the bigger picture, and describe to the public how their little corner of research is a small part of a much larger useful effort. For example, a researcher working on a new nanotech film may suggest that his work could one day be used to filter water for children in developing countries. This is a primary example of a futurist, even if the person doesn't call themselves one. Futurists go by many names - but in the end, anyone who looks forward more than about 5 years deserves to be called as such.