If you’re traveling outside the U.S. in 2009, here are two pieces of advice: Get or renew your passport now, and think twice before planning a car trip to Canada in June.

That’s when we may see the biggest change ever for Western Hemisphere travel.

Starting June 1 (unless Congress changes the deadline), Americans will need to show a passport, a passport card or other special document to return to the U.S. by land or sea from Canada and Mexico.

Despite assurances from agencies involved, there may be glitches and delays.

What you need now

Generally, you need a passport to enter the U.S. by air from any foreign country.

If you enter by land or sea from Canada, Mexico, the Caribbean or Bermuda, you may not need a passport, but you do need at least a birth certificate or other proof of citizenship, plus a government-issued photo ID, such as a driver’s license.

Children 18 or younger need only a birth certificate for land and sea entry from these areas.

What you’ll need starting June 1

The same rules apply for air travel — passport required.

If you’re arriving from Canada, Mexico, the Caribbean or Bermuda by land or sea, you’ll generally have several choices: a passport; a passport card, a new type of ID that the U.S. government began issuing in 2008; an enhanced driver’s license, a new high-tech version offered by a few states, or a “Trusted Traveler” cards such as SENTRI and NEXUS for frequent border crossers.

You’ll find a summary of the current and new rules at a Web site maintained by U.S. Customs and Border Protection, www.getyouhome.gov.

How to get the right stuff

The State Department’s travel Web site, www.travel.state.gov, (click on “Passports for U.S. Citizens”) is one-stop shopping for information on passports and passport cards. It has instructions and forms.

If you’re renewing a passport, you can download the form from the State Department Web site and mail it in. If it’s your first time, you can visit any one of thousands of “passport acceptance facilities,” such as post offices, to get what you need.

Go to a passport agency only if you need your passport in less than two weeks for travel or less than four weeks in order to obtain a foreign visa. You’ll need to make an appointment.

A passport costs $100 for adults and $85 for children younger than 16 (renewals are less); a passport card costs $45 for adults and $35 for children younger than 16.