Agile software development projects prioritize customer requirement changes and incremental feature delivery, adding value to both the customer and the business. Yet, the accommodation of such characteristics within the software development process may hinder the establishment of contracts between clients and software developers. For example, there's a mismatch between traditional project-contracting, which often emphasizes time and labor-hours, and agile methodologies, inherently outcome-oriented. This paper employs a mixed-methods approach, combining systematic literature review and qualitative research to identify and compare best practices for setting up contracts in agile software development projects. The aim is to establish an objective search algorithm for the compilation of relevant academic studies that research main practices, challenges, and components that influence agile contracting processes. At the same time, semi-structured interviews with agile practitioners were organized to investigate the best agile contracting methods used in practice. The literature survey findings align with the experts when acknowledging specific contract types (e.g., ‘Time and Materials’ contracts) as flexible frameworks for adapting to agile principles. However, the findings also indicate discrepancies between the academic literature and expert insights in terms of the factors affecting the contracting choices for development projects performed in agile manner.