In this chapter, we will focus on how to use OpenVPN on Linux, Windows, and Android. For each operating system, an entire chapter could be written to describe the intricacies of running OpenVPN in both the client and server mode, but as space is limited, we will focus only on the interaction of the OpenVPN client with the OS. The purpose of the recipes in this chapter is to outline some of the common pitfalls when running OpenVPN on a particular platform. The recipes focus mainly on the configuration of OpenVPN itself, not on how to integrate a working VPN setup into the rest of the network infrastructure.