My first advice would be to treat PMI as a process that really starts way before the closing. PMI is the set of actions that is intended to achieve the targeted goal of the acquisition, so having understanding of that goal (i.e., where we want to head to) as well as obstacles found during the M&A due diligence process that may derail getting to such goal (that would need to be fixed post close) would hugely affect the effectiveness and speed of the PMI. And then my second advice would be to understand that there is no magic to PMI; it takes a lots of planning, communication, and implementation, as is with all other M&A tasks (but more so since it is really akin to establishing new business operation within your organization). Third would be to be willing to take over the field where you do not typically do in normal operations, as there are many times where there is no clear definition of roles or who should be the right person to handle and make decision. Embrace it and try to lead in those circumstances. Common mistake is the lack of understanding on these key aspect of PMI, treating it as another assigned day-to-day task.