Take a look at your fact situation and pull out keywords. Question what is important and what is superfluous.
You need: Your fact situation
Turn keywords into legal issues of substance. What is your situation really about? Language Rights? Search & Seizure? Rule of Law?
You need: Toss the keywords into your favourite search engine, database, the catalogue. See what legal terms come out.
Focus on the legal issue here. Look into secondary sources to understand your legal topic and start collecting references to case law and statute law. Understand legal citation so you keep track of proper details in your references.
You need: Start searching the library catalogue, journal indexes, for secondary sources, which will lead you to your primary law. Study the McGill Guide so you will know what you need to put into footnote citations. Use databases to expand your searching and to collect documents.
Start reading! Apply the primary law to your fact situation. This is where you "think like a lawyer".
You need: Cases and legislation (maybe even some secondary authority) to apply back to the facts.
Write up your memo paper! Take time to articulate your points. Be a proofreader (or have someone else read it through). Take care with details like citations too.
You need: Refer to some books on how to write legal memos. These go beyond just how to organize your work. Find someone who is a good proofreader. It does not have to be a law student.