The purpose of this paper is to provide some guidance to users and potential users of longitudinal data sets who are trying to sort out appropriate approaches to the problems of analyzing longitudinal panel data. This paper does not attempt to offer any new insights into the methodologies available to estimate the determinants of change (or stability) in a given variable or set of variables over time, nor are the theoretical issues underlying these methodologies addressed in any detail. Instead, the paper is designed to be a much more basic "how to" guide, focusing on the most fundamental choices that must be made by the analyst in undertaking a project involving the use of longitudinal data. Further, the paper focuses almost exclusively on the application of longitudinal analysis to questions concerning patterns of family income, expenditures and/or demographic change.