Establishing password-less logins using public/private keys turned out to be a bigger pain in the butt than I had expected. There are a lot of resources on the web on how to do this, typically for BSD or Linux; and there are even scripts that purport to do this with assistance, but only the simple part. Whenever I do this, I have to pause and give this more thought that should be necessary, googlin' around for an answer to solve what I screwed up.
The problems are, there are always other components at play which are Mac-specific, and the guides are usually generic or aimed at Linux, BSD or some other sort of unix-like operating system. Even Apple's own documentation (from the Developer Connection, no less) is a little scant or can be intimidating for green sysadmins. This blog post is very long because it's very detailed. It's not quite step-by-step, but it's close.
A note: if there's an omission or an error in the instructions, and thousands of credit card numbers, Social Security numbers, cancer test results or SAT scores escape into the open, don't come knocking on my door.