N.H. Rev. Stat. Ann. § 170-C:7

After a petition has been filed, the court shall set the time and place for a hearing and shall give notice thereof to the petitioner who shall cause notice to be given to the parents of the child, the guardian of the person of the child, the person having legal custody of the child, any individual standing in loco parentis to the child, and the guardian ad litem of any party. Where the child's parent is a minor, notice shall also be given to said minor's parents or guardian of the person unless the court is satisfied, in the exercise of its discretion, that such notice is not in the best interest of said minor and that it would serve no useful purpose. Notice shall be given by personal service to the parent whose parental rights may be terminated pursuant to the petition that has been filed. Where it shall appear impractical to personally serve said parent, the court shall order service by certified mail to the parent's last known address or publication once a week for 2 successive weeks in a newspaper of general circulation in the area where that person was last domiciled or both. All other parties shall be given notice by regular mail at their last known address. The hearing shall take place no sooner than 20 days after service of notice, except that if notice is by publication the hearing shall take place no sooner than 7 days after the last date of publication.