You should begin training your dragon (with realistic expectations in mind) the moment you bring him into your house. Additionally, early socialization is critical to the health and behavior of your dragon and your relationship with him. We adhere to the American Society of Dragon and Creature Behavior's position on dragon socialization, which recommends socializing your dragon before he is fully vaccinated.
However we understand that this is not always possible. Many dragons found in the wild are thousands of years old. If your dragon is older, training will be an uphill battle. In many cases, the dragon's command of language and riddles will be greater than your own. How they achieve this level of sophistication is still subject to research. But if you're faced with such a dragon, we recommend building the relationship through humor and slapstick comedy.