An overview is presented of data analysis methods that can be used in surface analysis, especially those that can be used in x-ray photoelectron spectroscopy (XPS). The paper provides illustrations of the application of data analysis methods to real systems, and discusses practical problems that can arise when working with real data sets. The paper focuses upon curve fitting of core XPS data, and discusses the importance of combining curve fitting information with other supporting information and experiments. The effect of different backgrounds incorporated into the fitting process is discussed.