How do you build rapport with brokers?

We have worked with several Searchers across North America. It comes down to transparency and trust, regardless of whether you are a "Searcher" or not. If you see a listed opportunity that fits your criteria, explain why you are the best buyer. Sharing your one-pager on your investment criteria is helpful but not enough. As others have pointed out, a lot comes down to the basics of building a relationship.

Most importantly, respect for the broker's process and the time you demand from the broker. Do not expect the broker to show you off-market opportunities unless you pay a retainer or return the favor in other ways, like introducing the broker to sell-side opportunities that may not fit you. The buyers who succeed treat everyone they contact with respect, are punctual, communicate transparently and proactively, and do extensive background research on the industry, the broker, and the broker's firm, just like one would do when interviewing for a cherished job opportunity.

Typically, successful buyers have prior experience in the industry, know others (e.g., well-established lenders/investors) in the M&A ecosystem who can make warm introductions, preferably with letters of support, have acquired a business in the past, or know all the issues they should be prepared for and mitigants based on their strengths and weaknesses.

Lots of good ideas in here. For me, the more specific your search criteria (i.e., I want to be in this space because of this reason...) and you can portray that to my client (i.e., make the broker/intermediary look good in the eyes of the seller) the more at bats you'll get. Most sellers, while they like to know that their baby is not ugly (i.e., lots of NDAs), what matters more is quality versus quantity.