This document presents a synthesis of the  main challenges and lessons learned from the preparation process of intended nationally determined contributions (INDCs) by Parties to the UNFCCC in the run up to Paris. The challenges and lessons learned from the INDC preparation process hold great relevance for the next steps regarding the implementation and further development of countries’ nationally determined contributions (NDCs), in terms of both clarity and ambition. The report is based on the research NewClimate Institute (NCI) has conducted during the INDC preparation process, including two major surveys with developing country representatives before and after the process. Some examples are given for how to overcome some of the thematic challenges, which are drawn from GIZ´s work on INDC development with more than 30 partner countries.