Before filing a discovery or substantive motion, counsel should research laws governing the jury selection system, determine the proportions of the population in the various groups that are believed to be underrepresented, engage a social scientist or statistician to compile this data and obtain lists of jurors from the recent past. He or she should also observe potential jurors and talk with local criminal lawyers and selection officials. The form and content of the motion first filed in a jury challenge depends on jurisdictions' procedural requirements and other legal considerations. However, it must be somewhat general, should request inspection and copying of all records and materials, and provide an affidavit stating the facts leading to the belief that the system is invalid along with a memorandum of points and authorities governing a jury challenge. The discovery motion should include detailed affidavits by counsel, legal workers, and others describing how the system works, identifying any known illegalities, and presenting the results of the preliminary study. A jury composition study requires some knowledge of social science techniques and should have some limits on its scope. The most thorough method is to sample the qualified pool and all the nonqualified pools to determine their compositions. Date sources are the jurors' questionnaires, voter lists, driver registration lists, telephone surveys, and the census. Suggested strategies for the court hearing emphasize that the social scientist's testimony must define the cognizable group with clarity, demonstrate that it is sociologically and psychologically distinctive, and indicate its approximate size in the general population. The paper contains 22 footnotes.