This chapter presents an overview of customer lifetime value (CLV) modeling across different fields. It also introduces the challenges specific to free-to-play games across different platforms and genres. The chapter discusses the state-of-the-art solutions with practical examples and references to existing implementations. P. E. Pfeifer et al. point out a central problem present across the different research works on CLV: incoherent terminology. The reasons behind this problem are probably manifold, including the different research communities. Customer acquisition encompasses all activities aimed at getting new customers to start using the service or buying the products offered. As mentioned by Berger and Nasr and Berger et al., having an estimation of the CLV can help to more accurately decide on how much money to spend on a given promotional campaign and how much margin for profitability there could be in a new market segment.