in to / into
Two words versus one.
Into marks motion toward the inside: She walked into the hall. Write in to when in belongs to the verb and to begins the next piece: She turned the paper in to the clerk. Come in to warm up. Do not write into when in is part of the verb.
Examples
Use She walked into the hall.
Use She turned the paper in to the clerk.
Avoid She turned the paper into the clerk.