This paper summarizes the latest and/or most comprehensive data on important characteristics of homeless people. It looks at the demographics and distribution of homeless people among communities of different types, as documented by a range of research methodologies in various jurisdictions and nationwide. It also examines how characteristics may differ depending on the locations in which a study looked for people to include, and factors that seem to make people vulnerable to homelessness. The paper then turns to the need of local jurisdictions for information to help with service planning. It discusses the variety of people and agencies that might need information for planning, the types of decisions they must make, and what types of information would help them the most. It continues with a review of several strategies that work at the local level for collecting the most useful data, and the advantages and disadvantages of each method. Finally it draws the conclusion that every jurisdiction will be best served by gathering its own information about service needs for planning purposes. (Author)