Cases on TV are won through brilliant, impromptu cross-examinations at trial. Real cases are won through dogged investigation and by relentlessly investigating until you have both found and turned every goddamn page.
How do you do that?
First, ask your client to give you every document they have, and to explain what they are. Second, serve the opposing party with custom-tailored interrogatories and requests for documents asking for everything. You won’t get everything so, third, serve requests for admission demanding they admit those documents are all the responsive documents. That will get you more, but still not everything, so, fourth, notice the deposition of the records custodian for the defendant, at their place of business, with custom-tailored document classes identified. Fifth, when there, ask the deponent if they’re the most knowledgeable person about each class and, if not, ask who is, and then get that person to come down (remember, you’re already there and so are they), and ask them, and keep going until you’re confident you have everything you can get.
Did I mention you also need to scour the Internet, and to call other attorneys who litigated similar cases?
It’s a laborious, time-consuming process, and it’s not necessary for every case. But you need to learn how to dig for documents, and then, once you have them, how to develop the patience to “turn every goddamn page.”