Having language skills will certainly improve your chances at being hired by the US State Department. You can review the various embassy roles and positions on the State Department website for students at: https://careers.state.gov/intern/student-programs/. Check out the internship job descriptions for more information.
Look into taking the foreign service exam in February.
Be aware of international issues and politics by reading The NY Times.
Study abroad for a semester.
Be proficient in foreign language(s).
Get good grades and have involvement in school activities.
Keep your social media sites clean of any questionable posts or photos, ie, Facebook, Instagram, etc; since the feds will investigate/review to make sure you have a clean slate.
If accepted into foreign service you would be assigned to an embassy in the area of your degree. Consider applying for a new assignment every two years in different areas of the world, if you get in.