Applying for a passport should be as easy as signing on the dotted line. But with so many scenarios, from replacing chewed-up passports to expedited service, the process can be confounding. Here are some answers to common questions from travelers.

Q How much advance time do I need to apply for a passport?

AMonths before your departure date, and in some cases, even up to six months in advance, as some countries don't accept a freshly cut passport.

Can I apply by mail?

Not if you're a first-timer. Mail-ins are for renewals whose old passports are not damaged and were received within the past 15 years. The passport must also have been issued after your 16th birthday, and there must be no name change that you cannot legally prove.

To receive a new passport, send in a padded envelope a DS-82 form (available on the U.S. State Department's Web site or at post offices or travel agencies; see below); your most recent passport; two identical 2-by-2-inch passport photos; and a $55 check made out to the U.S. Department of State. If your name has changed, also include a certified copy of the legal document specifying the change (e.g., marriage license, adoption papers, etc.). Mail to: National Passport Center, P.O. Box 371971, Pittsburgh, Pa. 15250-9971.

You can also request a larger, 48-page passport for no extra fee; simply attach a signed request to your application. Your new passport should arrive within six weeks (for expedited service, see below). And yes, your dog-eared, stamp-plastered passport will be returned for future gloating purposes.

Who must apply in person, and what's the process?

Here's the checklist. If you answer yes to any of these, then head to your nearest passport facility.

* You are a first-time applicant.

* Your passport was lost, stolen or damaged. (If it was lost or stolen, you must also complete form DS-64.)

* Your old passport expired and was issued more than 15 years ago or when you were younger than 16.

* Your name has changed since your last passport was issued and you do not have the legal documentation to prove it.

* You are a minor, 14 to 17 years old. Parental consent or accompaniment may be requested, especially if the child does not have ID. (For younger children, consent by both parents or legal guardians is required.)

Application materials include form DS-11, but unlike the mail-in, do not sign it until the passport official gives the word; proof of U.S. citizenship, including a birth or naturalization certificate, among other official documents; personal identification, such as a valid driver's license or military ID; two 2-by-2-inch passport photos taken within the past six months; and payment of $85 (16 and older) or $70 (younger than 16).

Where do I go to apply in person?

There are about 6,000 facilities nationwide, including many federal, state and probate courts, post offices, libraries and county and municipal offices. The department's Web site (http://iafdb.travel.state.gov) will help you locate outposts in your neighborhood. In D.C., for example, the post offices at 1200 Pennsylvania Ave. NW and 4005 Wisconsin Ave. NW provide such services, but only during specific hours -- so check ahead.

I'm in a hurry -- my trip is in two weeks!

For expedited service, you can apply by mail or in person at a passport agency -- but only if you are leaving within 14 days. For the former, send in the requisite materials plus an additional $60 and overnight delivery costs. Write "expedited" on the envelope, and include your departure date and travel plans on the application. For the latter, make an appointment with a Passport Agency and bring with you all of the necessary documents, plus plane tickets or an airline itinerary and the extra $60. Tip: Due to occasionally fluky mail service, if you are leaving in six days or less, don't risk the postman and apply in person. In Washington, the center is at 1111 19th St. NW and is open weekdays from 8 a.m. to 3 p.m. You can schedule an appointment via automated service at 202-647-0518.

For even faster -- but costlier -- service, employ a private company that can deliver your passport in a jiffy, say 24 hours. Instant Passport, for one, lists turnaround times of one to six business days ($149, on top of government fees) and seven to 20 days ($109). Info: 800-284-2564, www.instantpassport.com. Other firms include American Passport Express (800-841-6778, www.americanpassport.com) and PassportsVisaExpress.com (888-596-6028, www.passportvisaexpress.com).

Where can I find additional help?

For advice or a status report on your application, contact the National Passport Information Center at 877-487-2778. For the State Department: http://travel.state.gov/passport/index.html.

Any other tips?

Be sure to fill out the emergency page of the passport. Then, make copies of your passport and pack at least one in your carry-on, along with two passport photos for emergencies. Also, jot down the contact numbers and addresses of the U.S. embassies or consulates in your foreign destinations -- you never know when you'll need an American friend abroad. And finally, be sure your passport is machine-readable; look for a series of numbers and/or letters and some unintelligible squiggles beneath your bio data.