This report is a discussion of various techniques for representing type information in dynamically typed languages, as implemented on general-purpose machines (and costs are discussed in terms of modern RISC machines). It is intended to make readily available a large body of knowledge that currently has to be absorbed piecemeal from the literature or re-invented by each language implementer. This discussion covers not only tagging schemes but other forms of representation as well, although the discussion is strictly limited to the representation of type information. It should also be noted that this report does not purport to contain a survey of the relevant literature. Instead, this report gathers together a body of folklore, organizes it into a logical structure, makes some generalizations, and then discusses the results in terms of modern hardware.