If you are from a country that requires a B-1/B-2 business visitor visa to enter the US, please plan for it early as government processing time constantly change.
Please visit the following website to learn more about the visa application process and timing for your country: http://travel.state.gov/content/visas/english/visit/visitor.html#overview . Current Processing times at the US Embassies and Consulates abroad can be found at: https://travel.state.gov/content/visas/en/general/wait-times.html/
Some travelers may be eligible to travel to the United States without first applying for a B-1/B-2 visa, if they are eligible for the Visa Waiver Program (VWP or "ESTA"). You are eligible to apply for admission under the Visa Waiver Program (VWP) if you: