
In the new expansion of Final Fantasy XIV, two new classes will be introduced: Red Mage and Samurai. In order to get them you won't have to go through days and days of plot quests and travel to new lands. You just need to be level 50 and talk to the right people.
Instead of unlocking classes in the new expansion zones, which can only be reached by level 60 characters who have completed the main storyline, both new additions can be made through quests in Ul'dah (one of the three initial cities). Any level 50 class can start the quest to become Red Mage or Samurai. The process is quite simple.
RED MAGE
The initial quest, Taking the Red, is located in the Steps of Thal, in the Ul'dah area, right inside the Gate of Thal. A young girl seeks help to save her sister from a gang of kidnappers. Sounds like a job for the first adventurer that comes along!

The kidnappers haven't gone far. Exit the Gate of Thal and after 10 seconds of running, you will face the bad guys. But... Who's the guy in red?

Apparently he is X'rthun Tia, the last of the Crimson Duelists, and the footage of his fight is short. Assassin? What assassin?

X'rthun has the situation under control, so you will return to Ul'dah to bring the girl back.

Since in Final Fantasy XIV you are the heroes of the game, X'rthun Tia has OVERY heard about you and, according to him, the red hat would look good on you. He will ask you to have a drink with him at Coffer and Coffin where he will ask you to...

Contrary to what happens in Heavensward, the new classes have one of the flaming new clothes. Draw your new weapon, put on your new clothes and you're ready for adventure!

Congratulations! You're now a level 50 Red Mage, ready to battle your way up to level 60 and discover what's new in Stormblood!
SAMURAI
If becoming Red Mage is easy, becoming Samurai is Easier still. The quest is given to you by a citizen of Ul'dah who is in the place where everyone appears when you teleport into the city. He's there, still, all caught up!

The man witnessed a battle between gladiators, in which an old man from the East beat everyone with a strange curved sword. It will lead you to the arena.

Once there, the NPC called "Silver-tongued Showman" will take you to the Gladiator Guild, where you will find Mr. Samurai sitting, waiting for you.

No drama. The old man thinks you could be a great challenger, so he'll give you a sword, a dress and a gem containing his brother's soul.

Easy, isn't it? And practical too! Since they'll be unlockable without going to the new areas, if you're at lv 50, you can simply change class and continue from where you stopped, before accessing the contents of Final Fantasy XIV Stormblood.