A nerdy confession: In law school, I tried to figure out what the legal research and writing instructor was talking about by reading real-life appellate briefs, which were kept in bound volumes in an unused portion of the library. I still believe that good writing often depends on starting with a suitable model.
Now you can find suitable models on the Internet. From Yale Law School comes a website devoted to compiling briefs and arguments from the US Supreme Court. Called the Curiae Project, it "provides Supreme Court records and briefs and other relevant materials free of charge on the Internet." (Link from Chris Geidner's post at De Novo.)