If the bank is a NA, there's no need to contact the secretary of state, as it can be served at the address listed with the FDIC, and no particular person is required to be listed in the summons.
For example, if you want to sue Bank of America, NA, you'll search "Bank of America," and then click "Bank of America, National Association" in the search results.
The address provided is acceptable for service.
There are process service companies that operate in every state, but county sheriffs are preferable because they're easy to find and reliable.
To look up the sheriff's office, simply perform a Web search for its Web site (they all have them) and then contact it using the telephone number on the contact page.
Once you know who is to receive the summons and complaint, contact the sheriff's office by telephone and ask: (a) how much for process service, (b) what form of payment is accepted, (c) how many copies of the summons and complaint are required, and (d) anything else that's required.
The sheriff's office will want a cover letter with instructions for service and an address for returning the processed papers to you.
Remember, every state has its own laws.
For example, in Oregon a process server (or sheriff) must serve a summons and complaint.
But whenever anything is filed with the court subsequent to that, copies must be provided to the other party(s) and counsel, if any.
For such documents, most courts require a "certificate of service" (a signed document certifying that documents were indeed provided to the opposing party(s) to be filed along with the original papers).
Some states, such as California, require that whoever signs a "certificate of service" not be a party to the action.
As always, check your state's laws and/or local court rules.
Many states have their entire database of corporate filings available online, while others charge a fee of $20 or so to look up the contact information of the agent for service of process, providing the information over the telephone and charging to a credit card.