Summarize:

Remove any paint, wax, sealants, adhesives, and debris. Be sure the subfloor is completely dry before beginning to install the parquet flooring. Use a belt sander to sand any high areas and/or fill any sunken areas with cement leveling compound. The subfloor needs to be smooth and level to ensure the overlaid parquet floor is level.
Clean the subfloor. Level the subfloor. Replace any damaged areas in the subfloor. Tighten any loose areas of the subfloor.