1. Author: This was his primary occupation. He wrote novels, short stories, essays, and travelogues.
2. Journalist: Twain started his career as a journalist, working as a reporter and later a columnist.
3. Lecturer: Twain was a popular public speaker and traveled extensively, giving lectures and readings from his works.
It's important to remember that "job" isn't always the best way to describe the work of creative individuals like Twain. He was a versatile and talented writer who earned a living through his writing and public appearances.