Internet mail is sent using a protocol called SMTP. You're somewhat familiar with this protocol if you've ever sent or received an email, because the "To/From/Subject/Date" values in each email are SMTP headers.
Most mail clients these days hide headers they don't recognize, including the ones from RFC-2369, but for seasoned users who are trying to figure out how to subscribe/unsubscribe or find list archives, they're there waiting for you.
Eventually, mail clients will begin to evolve (and some already have) and allow automatic built-in mail reader capabilities that let you subscribe/unsubscribe, etc. from a button in the mail client UI by using the features enabled by RFC-2369. But until the one you use provides that feature, here's how you can figure out how the mailing list experts "surf mailing lists".
The first step is to discover your mail client's "Long Headers" or "View Rich Headers" or "Raw Source" feature which will show you a wealth of SMTP protocol information for each message you've received.
Just about every mail client has such a feature. You may have to dig a bit to find it in your mail software, but it's probably there.
Once you're viewing the source of a list-generated email, you can verify the list you're subscribed to is RFC-2369-savvy if you see headers that look like the following:
These headers provide URLs or email addresses you can access to receive list help, to unsubscribe, to subscribe, reply-to/post, contact the admin, or access list archives, respectively.
There you have it... you never, ever have to ask anyone "how do I subscribe" or "how do I unsubscribe" to a list, ever again (so long as the list software you're using is RFC-2369 compliant anyway).