Every executive knows what a high-stakes game M&A talks can become. But even before the formal negotiations start, a one-on-one conversation that plants the seed of a deal or a back-of-the-envelope sketch of the business case for it may present deal makers with conflicts of interest and strategic vulnerabilities. Who would get what value from a deal? Who would govern the new entity? What legal boundaries must prospective partners be careful not to cross? Moreover, deal makers also know that failing to close a transaction can turn today's potential partner into tomorrow's better-informed competitor.

Tension often grows as each company increases its investment in time and advisers. The longer negotiations go on, the more anxiety builds to complete the deal—if only to avoid the embarrassment of failing to deliver it. Transaction costs rise, constraining a company's ability to capture synergies and in some cases even causing good opportunities to vanish.

To successfully navigate the complexities of even the earliest discussions about mergers, acquisitions, and joint ventures, some companies are borrowing an approach that merger specialists sometimes use much later in the process to expedite postmerger integration plans and business strategies: they appoint a clean team. In the preannouncement period, such...