Once a decision has been taken that it is either desirable or necessary to innovate, or at least that there are weaknesses or deficiencies to be remedied in the present system, among the factors which require early consideration are, first, where the particular innovation will come from, and secondly, how it will be introduced into the school. In relation to the innovation, a number of sources may be available to the innovator. There may be a nationally published project or course that could be considered; another school known to the innovator may have adopted an innovation that could be looked at; a group in a local teachers’ centre may have developed an innovation in a relevant area. If these or other sources are not fruitful and nothing considered appropriate is already in existence, teachers in the school will have to develop their own innovation. On the other hand, in some instances a school-developed innovation may be the first choice. Innovations developed or disseminated in these different ways tend to have distinctive characteristics; a study of the bases on which innovations are developed, disseminated and utilised, that is, models of innovation, will help in the identification of possible strengths and weaknesses of the alternatives that are available.