Legal Question in Civil Litigation in California

You don't need to subpoena parties at all. Subpoenas are only for non-parties. You can accomplish what you want by serving an a request for production, and then later serving a notice of deposition. Just make sure you don't miss the discovery cutoff or other key dates.

A subpoena is not what you are looking for. That is an instrument designed for someone that is not the opposing party(s).

You serve a request to produce. Then, you serve notice of the deposition. Make sure you do it in time because there is only a certain amount of time you have to do this through what is called discovery.

Some people tarnish their entire cases because they miss the cutoff times in making a request for production and/or the notice of deposition.