Said summons shall be served by the city marshal, any member of the police force or any constable of the city, at least 5 days before the return day thereof, upon all the respondents found within the county, by exhibiting the original and delivering a copy to each of them. If any respondent who is a resident of the county cannot be found, the summons shall be served by leaving a copy thereof at his or her usual or the last place of abode, with some person of suitable age and discretion. If any minor or person of unsound mind is interested in the premises to be taken, service may be made on the guardian of such person, if any, and if there is no guardian, the probate court may appoint some discreet and proper person to be guardian ad litem of such person in such proceedings, and such guardian shall have authority to represent such person in said proceedings. The proceedings to appoint such guardian shall be the same as in other cases provided by statute. If it shall appear on the return day of the summons that any respondent cannot be found within the county and has not been served in the manner provided, or is non-resident and has not voluntarily appeared, the court may make an order requiring such respondent or respondents to appear and show cause why the prayer of the petition should not be granted, on a day to be named in the order, and not less than 30 days from the date thereof, and may require that a certified copy of such order be personally served on such respondents wherever found, if practicable, at least 6 days before the time named in order for appearance, or the court may make such order for appearance and require as to any or all such respondents who shall not have been personally served and have not appeared, that service be made by publishing a certified copy of such order for 3 successive weeks, at least once in each week, in at least 1 newspaper published within the municipality, the last publication to be at least 6 days before the day fixed in the order for appearance. Alias and pluries summons may be issued, and the probate court may adjourn the proceedings from time to time as there shall be occasion, and as in other civil cases. Service of such order for appearance in either mode described shall be sufficient notice of the proceedings to bind the respondents and the property represented by them. The return of the officer upon the summons and an affidavit of the due service or the publication of the order for appearance, if any, shall be filed with such probate court before a jury shall be impaneled, and be sufficient evidence of service on the respondents and of the manner of service.