I believe that some key challenges that project managers face are managing expectations of all project stakeholders, poor communications and scope changes (creep). The best way to deal with the first two is through proper stakeholder analysis, stakeholder engagement through solid and clear communication plan. As for scope creep, the more you spend time articulating project scope and requirements upfront, through a solid scope statement as well as engaging all stakeholders on various scope definition techniques (such as the affinity diagrams, work break down structure, and deliverables register), the less your project would be susceptible to scope creep.