A survey is given of the main techniques in parameterized algorithm design, with a focus on formal descriptions of the less familiar techniques. A taxonomy of techniques is proposed, under the four main headings of Branching, Kernelization, Induction and Win/Win. In this classification the Extremal Method is viewed as the natural maximization counterpart of Iterative Compression, under the heading of Induction. The formal description given of Greedy Localization generalizes the application of this technique to a larger class of problems.