When tackling a case I always recommend learning the issues before going over the facts. Learning the issues includes going over the relevant law related to the case. Most attorneys prefer to spend a lot of time going over the facts and investigating their case before they know why its relevant, which leads to spending a large amount of time learning facts that are not relevant to your case.
ISSUE BASED INVESTIGATIONS ARE MORE FOCUSED
By understanding the legal issues of your case it will allow you to focus your investigation on the more important facts, while ignoring the less relevant facts. For example you might not look at the date of a document unless you know the date is important. It also helps you obtain more relevant information in your investigation. For example if you're interviewing or deposing a witness you will be in a better position to make sure you're asking the right questions.
FOCUSING ON THE ISSUES WILL IMPROVE YOUR LITIGATION SKILLS
By focusing on learning the issues of a case you will also improve your litigation skills. Legal issues tend to arise over and over again, and after learning a case's legal issues you will probably want to put together the theory, themes, and methods of proof of the case. By focusing on issue spotting and putting together your theory, themes, and methods of proof on a more regular basis your will improve these skills.