You may may earn one of these mounts by using the Recruit-a-Friend (RaF) button on your in-game friends list to successfully recruit someone to the game. The recruit must pay for two months of game time before you can claim a reward. Once you're eligible, after a delay period*, an automated in-game service will direct you to a window where you can choose a mount (or pet) reward.
*Note that if your recruit signs up via subscription there may be a delay of many weeks (or months) before billing occurs and you can claim your mount. In our experience, the procedure seems to be much faster (only about one week) if the recruit applies two months of game time codes instead.
It is even possible to 'recruit' yourself by using your existing Battle.net email address on the RaF form. Wait for the recruitment email, set up a new WoW account under your existing Battle.net account, pay for two months of subscription, and (after the delay period) claim your reward.
Trading Card Game Loot Codes
World of Warcraft Trading Card Game (TCG) booster packs may contain rare 'loot' cards with special codes that can be redeemed for mounts and other in-game items. While the TCG has now been discontinued, cards are still currently available via third parties such as WoW TCG Loot, WootLoots and eBay. Keep in mind, however, that the longer a TCG card has been out of print, the more expensive and harder it will likely be to find.
Loot codes are not currently redeemed on your Battle.net page; the procedure is far more complicated! You must first enter the code at the Promotion Code Retrieval Page which generates a second code which you must supply to Landro Longshot in Booty Bay in order to receive the mount. Be sure you select the right region and realm!