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I really don't know how you could guarantee such a thing. There are probably agents who do such things. I would think that even so there must be an element of trust.
If ytou are buying a domain name get access to the account the registrant has with registrar, change the password and (all of) the email addresses and contact info in the whois record for the domain name. You may also have the registrant "push"(an internal transfer) the name to an account you and you alone have access to. If you are the seller get your money first before you make any of the aforementioned changes. In either case you may use a neutral trusted third party which is a great but sometimes expensive way to go.
Escrow.com is any doubts.
Wire transfer if a confirmed big league player. Forget the escrow fees. They don't need the bad P.R. and they tend to be very savvy businessmen, "a deal is a deal and my word is my bond" class of men. Nice to know the business world still works that way.
Get on the phone. I've also had people transfer domains before payment. Probably doesn't hurt that my other job is legal eagle. Most people can appreciate that I'm not going to skip town with their domain name.