New Hampshire Legal Aid's article tells us that the best way for tenants to protect themselves from rent increases is to have a written lease, and the Attorney General's Consumer Sourcebook reminds us to read those leases carefully since they can include clauses that force mid-lease rent increases. Both websites are great sources of information for landlords and tenants and are linked to below.
Please remember that this guide is for information purposes only and is not comprehensive. It is intended as a starting point for research, to illustrate the various sources of the law, and to provide guidance in their use. NH Law About ... is not a substitute for the services of an attorney.