Participating in research and development projects designed to increase the profitability and social outcomes from livestock production in smallholder crop–livestock systems provides valuable and rewarding learning experiences for scientists from Australia and partner countries. The majority of livestock in Asia are in these systems and any interventions to increase animal production need to consider the cropping activities of the farm, which vary considerably in relation to people, land and water resources, season length and the number and types of crops. Understanding the farming systems in enough depth is essential if interventions are to lead to improved outcomes for families. In this paper, we briefly consider the diversity and complexity of crop–livestock systems and the approach of the Australian Centre for International Agricultural Research in investing in research, development and extension for positive impacts from livestock production on the wellbeing of rural households in developing countries. An important approach to categorising livestock farmers to assess whether they are likely to be receptive to change is described. Consideration is given to the appropriateness of technologies, the need for sound science and the importance of capacity development in underpinning useful changes to systems. Because of the diversity and complexity of systems, systems-modelling is important in exploring options and interactions between components of the farming systems. Examples are given throughout the paper to emphasise learning from experience. The paper concludes with a list of the lessons learnt.