When travelling overseas you need a valid, unexpired passport. Some countries require visitors' passports to be valid for a number of months beyond the intended period of stay.
If you are travelling on a passport issued by a country other than the country where you live, check whether you will need a re-entry visa allowing you to return.
Check your passport for any signs of damage which may make it invalid for travel. If you have any concerns, contact your local passport issuing office.
Passport requirements for travel to or via the USA under the Visa Waiver Programme changed in October 2006. See if your passport is eligible.