Science is one of the most useful resources in the game, as it unlocks new techs, buildings and military units. Science does not need to be spent, like the production resource, however your research as to be selected in order for your scientists to know what they’re meant to be researching!
To set what you want to research, click on the icon of the test tube type icon (It’s blue) and select from the tech tree. If you’re in a civilization with others, it’s best to mouse over each tech and see what your fellow members are researching and choose that – this will lead to a decreased research time as your research will be combined.
What I am for when really trying to research science is a university and town square next to each other, surrounded by scientists. This seems to be the ideal layout for getting the most science out of each scientist.
Of course, if you have a better technique, please comment and let us know!