How to become an expert in your research field?

Assess yourself against the list of specialties in your field.
Read books, blogs, periodicals, and sites.
Join, participate in, and help lead communities of practice in your field.
Successfully complete relevant training.
Attend conferences in your field.
Find a mentor.
Learn by doing.
Stretch your limits by volunteering for and accepting challenging internships, apprenticeships, assignments, projects, and missions.
Present, speak, lead discussions, and deliver training.
Post, write, and publish.