In all cases of notice by publication, the newspaper shall be selected by the petitioner or other person required to give such notice. In all cases requiring notice, whether by publication, mailing or otherwise, proof by affidavit of service of notice and, unless excused by court order, a copy of the petition and any attachments to it shall be filed before the hearing. No defect in any notice or in its service, not affecting the substantial rights of the parties, shall invalidate any proceedings after such notice and the proof of its service have been approved by the court.