Characters must choose a Style upon reaching Rank 3 in a Weapon Skill(with the exception of Exotic Weaponry). At character creation, the cost in OP is dependent upon the character's Homeland, and is listed with the Style description.
When a character reaches Skill Rank 3 during play, they may choose to spend XP to learn a Style from any available master, paying the lowest listed cost. However, this usually involves doing a favor for the master or the country that he is from. Anyone with a Skill Rank at least 1 higher than the character can serve as a master, with the exception that a master with Skill Rank 5 can teach a character advancing to Rank 5.
Learning a Style immediately grants the user access to their Style Bonus, if the Style has one. This Style Bonus normally applies only when using the weapon associated with the Style. Style Bonuses that are obviously generic in nature, such as the Valtan immunity to fear, apply even when the character is not using the associated weapon.
Example: Victor Northcliff just raised Swordsmanship to Rank 3. Being from Alden, if he had done this during Character Creation he would have needed to spend 30 OP to learn Valtan BattleDancing. However, he has already started play, and recently aided in the rescue of the Valtan Princess, Alia. The King of Valta grants him a boon, so he requests to be trained in Valtan BattleDancing. Victor pays 15 XP, not 30, as that is the lowest cost listed.