Each time you enter the United States, you will need a valid visa in your passport. The application process varies by location. Review the U.S. Consulate website to learn of specific rules and the most current application procedures.
It is possible to get a new visa at a U.S. Consulate that is not in your home country. Be aware that you are applying as a "third-country national" when you do this. There may be additional items that you need to present to the Consular Officer. It is generally simpler to apply in your home country.
There are some instances where you can get a subsequent visa without another interview. Review the U.S. Consulate website for current information regarding eligibility.