Biological macromolecules can be crystallized by a variety of techniques, and using a wide range of reagents which produce supersaturated mother liquors. These may, in turn, be applied under different physical conditions such as temperature. The fundamental approaches to devising successful crystallization conditions and the factors that influence them are summarized here. For the Novice, it is hoped that this brief review might serve as a useful introduction and a stepping-stone to a successful X-ray structure determination. In addition, it may provide a framework in which to place the articles that follow.