Discovery ends 30 days before trial (the cutoff date). That means, at the very latest anything you ask for must be due 30 days before your trial. At the latest, you need to serve your requests 60 days before your trial date (65 if you serve by mail).
Requesting documents requires a different kind of discovery process. How many questions can I ask? If your case is a limited civil case ($35,000 or less) you can request up to a total of 35 combined request for admissions, form interrogatories , special interrogatories, and requests for production.
In the United States, discovery is mostly performed by the litigating parties themselves, with relatively minimal judicial oversight. The Federal Rules of Civil Procedure guide discovery in the U.S. federal court system.
If the parties are having a dispute, either party can file a motion with the court asking the judge to order the other side to respond to discovery requests or punish the other side for failing to respond to discovery requests or for making unreasonable discovery requests.
If you want to file a motion, the process is generally something like this: You write your motion. You file your motion with the court clerk. The court clerk inserts the date and time your motion will be heard by the judge. You “serve” (mail) your motion to the other side.
In certain cases, you might be able to write a letter to the other side and request the documents that you need. However, in more formal cases, you will likely have to draft more formal discovery demands. There are usually forms available for this in local law libraries, from the court clerk's office, or online.
Discovery materials are, for the most part, understood to be public so long as filed with a court; otherwise, they are not necessarily accessible.
If you don't respond within the time given, the opposing party may file a motion to compel your compliance with the court.