About sharing the achievements / pet / mount systems is still in beta. The FAQ of new Achievement System on the March 5th still have no explanation of corresponding achievement sharing system. There are a great number of guess about the system on the forums of foreign severs. At present the more consistent understanding is that all the achievements / pets/ mounts of your characters also belong to your accounts'. However not all the achievements / pets/ mounts of your accounts can become the achievements / pets/ mounts of your characters'. A character with level 1 can not gain the achievement of level 85. That is to say that only when your character meets the requirements of the achievements, you are able to gain this achievements. For example a new character which is only level 1 can finish the achievement called World Explorer. So if this achievement has been listed in your account achievements, the achievements list of your new characters also will have the achievement.
Players care most about some rare kinds of achievements such as the fifth elements, the first kill of server and the first occupation and profession of level XX as well as the PVP title in the 60s. Here it comes that there is still no unified conclusion whether the titles can be shared at the moment. The official still has no introduction so it is hard to say whether they can been shared.
World of Warcraft is really a excellent game. And it has a great number of players. They are all crazy about playing it. I have ever discussed with some players who have been played WOW for several years and they all have more than one account. These players who are playing game care most about of the WOW gold which can help them play well in the battles with their enemies.