Most introductory textbooks in Operations and Supply Chain Management offer a good discussion of forecasting models. Techniques such as time series models, regression, and measures of forecasting accuracy are routinely covered in these books. One possible source:
Cecil Bozarth and Robert Handfield, Introduction to Operations and Supply Chain Management, Prentice-Hall, 2006. ISBN 0139446206
Planners who are interested in a more advanced treatment of forecasting might want to check devoted to business forecasting. One possible source:
John Hanke, Arthur Reitsch, and Dean Wichern, Business Forecasting, Prentice-Hall, 2001. ISBN 0130878103.