The phases of ISO 9000 certification consists of two parts i.e., documentation and certification.
The documentation part can be done in house or by the help of a consultants. Normally every company takes the services of a experienced consultant to develop and introduce the system.
The certification is done by an agency accredited in this regard. The certification agency normally divides into activities into two parts documentation review which may be done with or without visits to your works and compliance audit which is conducted at your site.