I'm going to start a series on working with legacy code based on some of things I have learnt over the years. First I define my terms for 'legacy', I define legacy as (as someone on twitter called it) not brownfield but blackfield. Brownfield can be code you did yesterday, last week or last month etc. Blackfield tends to be a great older (think years old) and worked on by a great deal many people. Sure brownfield can also be legacy code but often has far less smells and technical debt, due to it's age the problems are often far worse and far harder to treat.  I'm not sure how many posts I'll write for the series or how long it will run for but I'll add them as and when they occur to me. Finally if you are working with the kind of codebase I describe then Michael Feathers 'Working with Legacy code' is a great resource.