This chapter explains the use of psychological theory within a nursing framework to guide them how to assess patients' lifestyle behaviours and how to provide guidance on changing their behavior in day-to-day clinical practice. One way of identifying the problems associated with changing behaviour is to ask the patient to list the advantages and disadvantages of each of the behaviours they are trying to change. Rewards are an effective way of changing behaviour and these can be anything of value, such as praise or treats. A detailed action plan of how people are going to change their behaviour can help to find what they are going to do, and where they are going to do it. The chapter suggests nurses to encourage the client to do most of the talking, and should use open questions to evoke confidence talk. They also should ask for potential obstacles and putative coping strategies to review obstacles and how the client has overcome them.