Since I already have ten characters on my home server, I have to wait for the expansion to come out to 'reserve' my name.
/sigh

Tip: You can create a "starter" account that doesn't expire, and use that to "reserve" names on your chosen server. Though that would most likely only protect it from casual namecheckers, who give up after the "That name is unavailable" message. Players can still petition GMs to ask to free up names. I'm guessing that, being on a free account instead of a paid account, they'd be more likely to do a forced namechange in hopes that someone else would pay extra money for a namechange.

(You can also run two wow clients simultaneously; get a toon on your server/faction up to 10 and invite it to a group from your main account, can then convert to a raid for an easier time getting into old instances without having to bug friends/guildies. For performance reasons, you can quit the other client after the raid group is formed.)

A warning for reserving names with starter accounts though, if you create it in your main Battle.net account (which is easier if you also use that account to form raids for soloing old content)
Once you *log into* a character, their mailbox is filled with all the CE/store pets your account has purchased, but you cannot access the mailbox on a starter account. Since you can't delete a character with mail, you'd have to wait 30 days for those mails to expire before you can delete the character.
So either don't log into the character after creating it, or reserve the name long before (in this case) the release of the expansion so that the mailbox is empty again.

A friend of mine did me a kindness and reserved the names I wanted on her own account (she has characters on many different servers, but not too many on mine.)