To enter Mexico, you will need a valid passport. Citizens other than U.S. or Canadian may have other requirements such as a visa. Please contact a Mexican consulate or embassy near you.
For those of you entering on an airline or cruise, your identification must be presented at the airline/cruise check-in. Once on the plane/ship you will be given two forms to fill out – one for Immigration (Tourist Card) and another for Customs (Customs Declaration Form). There are restrictions as to what you can bring to Mexico. Some of these restrictions are limits for “duty free” and some are absolute, such as firearms without a permit, not to mention drugs (do not bring either into Mexico).