An alternative to the auction (where a domain is offered for sale at a fixed point and time period) is a domain broker.  In return for a commission -- typically 5-20% of the purchase price -- the broker will actively solicit buyers for your domain.  For a premium domain, this seems like a very worthy service, because the "best fit" buyer may not even be in the domain business, and bringing this person to the table may create enough value to more than pay for a broker's services.

Many brokers also can provide an escrow service or domain parking.  Brokers frequently require an exclusive agreement for a longish period of time, typically 3-6 months.

My question: How does one find a top-flight domain broker (as opposed to one who doesn't have the necessary contacts and skills)? 

I haven't seen any top ten lists for domain brokers.  Perhaps there never will be, because even a top broker might not sell too many domains in a year...  I'm sure many of the large private sales of recent years were brokered by someone, but aside from one or two references that a particular sale was brokered, it's almost like this business -- publically, at least -- doesn't exist!

Is calling the purchasers in recent big private transactions and asking "how did you meet up with the person who sold you the domain" the best way to do this, or am I overlooking something?