The time to respond to a Demand for Admissions is 30 days. If the Defendant does not respond in that time, the admissions can be deemed "Admitted" by the Court. Often, a defendant will deny having received the Demand for Admissions, and thus it is recommended to serve it via certified mail return-receipt-requested (green card). The Rule is Court Rule 4:22-1 and is available at www.judiciary.state.nj.us under the Court Rules heading. As for Interrogatories, the time to answer is 60 days. The Court Rule is 4:17-4.
Please note that these discovery Rules have many exceptions based on the timing of the filing of the Answer, service of process, and other factors. I have answered your question as to where the Rules may be found. Other typical discovery requests would include a Demand for Production of Documents and a Demand for Insurance Information if applicable. It is always best to consult a local attorney.
Good luck, Adam Springer.
While I strongly recommend to consult an attorney since the rules of civil procedure and discovery process is quite complicated, you can find responses to your questions in NJ Rules of Court (http://www.judiciary.state.nj.us/rules/). Rule 1:5-2 describes the manner of service of documents other than initial pleadings. If a defendant is represented by an attorney, the service of interrogatories can be done by an ordinary mail. Rule 4:17 summarizes all requirements and timelines for interrogatories.
Disclaimer: This answer should not be relied upon as legal advice. I am admitted in the States of New Jersey and New York and before the United States Patent and Trademark Office only. The response above does not form an attorney-client relationship, nor it is intended to be anything other than the educated opinion of the author. Consult an attorney in your geographic area before you act on any of this advice.
You need to hire a lawyer, or at least buy a good guide, because the statistics show, as does common sense, that people representing themselves don't do well against lawyers, and if you're serious about your case, you'l treat it as such and hire a professional who knows the substance and procedure involved in your case.
There are many rues and deadlines you need to know. Linked below are some sources.
Disclaimer: I'm only licensed in CA. Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.