A "best practice" is a method or process that practitioners recognize (usually through experience and research) as being more effective at getting the job done than other methods (or processes).
While frequently used as a buzzword to describe good ideas, most "best practices" actually help folks get the work done more reliably, efficiently and effectively than average. Please keep in mind that a "best practice" for one industry is not necessarily the best way to get the job done in another industry. The "Joel Test" gives a number of examples of features of software companies that many people have come to recognize as "best practices"; for example, a continuous integration system would pass both steps 2 & 3 of the Joel Test at once.
