Little attention has been paid in the literature on "how to implement" software process improvement (SPI) which has resulted in limited success for many SPI efforts. In this paper we report on our recent empirical study which explored the experiences and perceptions of practitioners about SPI implementation. We visited 11 companies and conducted 14 in-depth interviews. Using the different experiences and opinions of practitioners regarding SPI implementation, we have developed a model for the implementation of SPI programmes. This model has six phases - awareness, learning, pilot implementation, SPI implementation action plan, implementation across the organization and maintenance - and provides advice to practitioners in effectively implementing SPI programmes.