Does everyone understand the reason for the transition - It is incredibly common to underestimate the power of communicating the reasons for change. Sit down with your team and walk them through the changes. Solicit feedback to see if your team sees other improvements or even potential changes to your plan.
Do you have the right people - In order for any type of transformation to happen, you need to have a team that is open to change. During a transformation, passionate team members are great at accelerating and embracing change. The flip side of that is that certain people might act as an anchor, creating friction. If this happens, make sure to sit down and walk through with this person why they are having a challenge with the change, and what you need and expect from them.
Does your team know what to do - Does each person know what is expected of them in the new model? If you are going to start requiring burn down reports, who is creating it and how? Did you or someone else train them? How will their performance be evaluated after the transition?
Initially focus on communication - A lot of potential problems are caught early when you emphasize communication on teams. If you are transitioning to Agile, it is likely you are removing some level of documentation your teams are used to. This could create gaps in shared understanding. While you are still transitioning, it is critical to emphasize that your team needs to over communicate during the change. Give your team permission to spend more time and effort on alignment and communication.
Change how you evaluate people - Employees tend to focus on what makes their boss happy and what gets them compensation changes. When you transition, make sure you work with your management staff to map out how these changes will impact how employees are evaluated. Previously, a PM might be evaluated on their ability to create a thorough project plan. After a transition, they might be evaluated on their ability to help create and manage a backlog. Does your manager realize this? Is the manager able to provide feedback and training to their employee if they have issues? Does the employee understand how their performance will be evaluated after the change?