Survival guide for maintaining legacy systems

All systems have some degree of legacy, starting from the new one that you are creating just now, up to the one that has been abandoned for years but still keeps one critical active user somewhere. At some point in your career as a developer, you will inevitably end up maintaining a system that you didn't write, and which you don't know much about. What are your options? Are there tools and techniques that can make you work easier? Yes, there are! In this talk I'll go over different approaches that will improve your experience dealing with a legacy system, and also, a set of recommendations for preventing future systems becoming legacy.Slides