First of all you can apply for the ESTA only if you meet the following requirements
1. You have a valid passport and national of a country participating in the visa waiver program.
2. You do not have a visitor visa
3. You plan to travel for less than 90 days
4. Your travel is for business or pleasure purposes.
The following countries are a part of the Visa Waiver program as of March 2009. Always check before you apply.
Andorra, France, Luxembourg, Singapore, Czech Republic,
Austria, Germany, Monaco, Slovenia, Estonia ,Australia
Iceland, Netherlands, Spain, Hungary , Belgium. Ireland
New Zealand, Sweden, Latvia , Brunei, Italy, Norway, Switzerland
Lithuania, Denmark, Japan, Portugal, United Kingdom, Slovakia
Finland, Liechtenstein, San Marino, Republic of Malta, South Korea
If you are a citizen of the following countries you need a electronic passport : Czech Republic, Estonia, Slovakia, Hungary, Latvia, Lithuania, Republic of Malta, and South Korea
Otherwise you need a machine readable passport, based on the date of issue or renewal. Check the ESTA website for the most recent rules.
The application is done online from the US goverment web site at http://www.cbp.gov/xp/cgov/travel/id_visa/esta/
The details are simple and have your passport and travel information handy.
