Except for econometricians, most of us usually have one or more books they refer to when we want to get a first-hand reference on some basic or advanced topics, and/or get some basic understanding or key information on some topics.
Mine is 'Estimation and Inference in Econometrics' by Davidson and MacKinnon; it helped me review some basic or more intricate theoretical and practical aspects, and get an opinion on some issues on which no consensus has been reached.
I'd be glad to find out which reference do you use, and what are its strong parts and weak parts.