During the last years, most of the large free / open source software projects have included code review as an usual, or even mandatory practice for changes to their code. In many cases it is implemented as a process in which a developer proposing some change needs to ask for a review by another developer before it can enter the code base. Code reviews, therefore, become a critical process for the project, which could cause delays in contributions being accepted, and risk to become a bottleneck if not enough reviewers are available. In this paper we present a methodology designed to analyze the code review process, to determine its main characteristics and parameters, and to detect potential problems with it. We also present how we have applied this methodology to the WebKit project, learning about the main characteristics of how code review works in their case.