LANGUAGE: English is widely spoken in most cities across Southeast Asia, and even in remote areas, you can usually find English-speakers in hotels. Menus are typically printed in English and the local tongue, and museums usually have information in a number of languages.
SAFETY: Use common sense. Leave expensive jewelry at home; stash what you don't need for the day in your hotel safe; safeguard passports and airline tickets; beware of carrying valuables in a backpack, as they can be sliced open without your knowledge while you're crossing the street or waiting for a train.
MONEY: ATM machines are not always plentiful, so bring travelers checks as well as a few hundred dollars in small bills. U.S. dollars are almost always accepted if you're stuck for local currency.
VISAS: Be sure to check far in advance on whether you need to arrange visas to enter the countries you're visiting. And just because visas are available on-arrival at airports, don't assume the same is true if entering via land borders. Also, if you plan on leaving and coming back, inquire about whether a multi-entry visa is necessary.
HEALTH: Visit the Centers for Disease Control and Prevention's Web site at www.cdc.gov/travel/ for updated information on health threats like bird flu and SARS as well as the recommended vaccinations for traveling in the region. Keep in mind that some countries will not allow travelers to board planes with a fever, so if you develop flu-like symptoms, it's a good idea to get checked out by a doctor.