By now, you've learned all the differences between Global Entry and TSA PreCheck, and are ready to bite the bullet and commit to one. Since Global Entry includes TSA PreCheck—and is only $15 more than PreCheck—you decide to go with it. Smart move. But now you've actually got to apply. What to do next?

First: Make sure you're eligible.
Wait, you can be ineligible? Sad but true—you have to earn the government's trust to be part of a "Known Traveler" program that will get you through customs and immigration in a breeze. Here's who can apply for Global Entry: U.S. citizens, U.S. permanent residents, and citizens of Colombia, the United Kingdom, Germany, Panama, Singapore, South Korea, Switzerland, and Mexico. (Depending on the country, visas may be required.) Canadian citizens and residents are also eligible for Global Entry benefits through membership in the NEXUS partnership (the agreement that allows members expedited processing when entering the United States and Canada). The Netherlands has an arrangement for its citizens via FLUX, its trusted traveler program. Only Americans can get the PreCheck benefits, though, and anyone under the age of 18 must have parental or legal guardian consent to participate.
If you have a criminal record; provide false or incomplete information on your application; have pending criminal charges; have violated customs, immigration, or agricultural laws in any country; are currently being investigated by any local, state, or federal agency; or are inadmissible to the U.S. under current regulations, your application may be denied. For questions about eligibility, contact the Global Entry Enrollment Center nearest you.

Next: Create an account online.
All applicants, regardless of age, have to create a Global Online Enrollment System account. (It's "GOES" for short.) This is where you can submit an online application, along with payment. Understandably, the application is extensive: In addition to personal information—name, email address, gender, eye color, height, language preference—it requires you to fill in your employment, travel, and address history over the past five years. It also asks if you've violated any customs or immigration laws or been convicted of a crime. Fill out the application and submit a $100 fee, which covers your five-year membership if approved, but is non-refundable if your application is rejected. You can pay by credit card or electronic bank transfer.

Schedule an interview.

Once your application is conditionally approved—expect an answer within three weeks—you'll receive an email that there's a message in your GOES account. You'll then be asked to schedule an in-person interview at a Global Entry Enrollment Center within 30 days. Enrollment centers can be found all over the country: expect to get an appointment within a month or so, but check back often, as people may cancel their appointments, and an earlier slot could open up.

Note that some of the least crowded enrollment centers are at airports. As part of U.S. Customs and Border Protection's "Enrollment on Arrival" program, you can even eliminate the need to schedule an interview at an enrollment center—when you land, just follow the signs to CBP officers who will complete your interview. Here's a full list of "Enrollment on Arrival" airports across the country.

Prepare for that interview.
Pack a valid passport and another form of ID like a driver's license or ID card. Print the conditional approval letter in your GOES account, just in case, and set aside documents that show proof of residency—think a utility bill or rental agreement. Oh, and in case something like this matters to you, consider your appearance the day of: You'll be getting your photo taken at the interview, and this headshot will go on an ID card.
It goes without saying, but: actually show up for your interview.

The good news is that if you're conditionally approved, most of the hard work is over—you've already been pre-screened, and your information has been checked by the government. Most of the questions you'll be asked are ones you've already answered on your application, or ones officials already have the answers to, like: "Why do you want to join Global Entry? What do you do for a living? Where have you traveled in the past five years? Have you ever been arrested, or had an issue at customs or border patrol?" Still, take the questions seriously and answer them as you did on your application. It's almost time to celebrate, we know, but don't ruin everything with a joke.

At the appointment—which will last anywhere from 10-15 minutes—you'll also have to provide your fingerprints and get your photo taken. Within a few minutes, you'll be confirmed for Global Entry, and will be given a Known Traveler Number (KTN) that you can start using immediately to be eligible for TSA PreCheck. An official Global Entry card will arrive within two weeks—just make sure to activate it within 30 days. You won't have to show this card at the airport, though, as it's only for land and sea ports of entry.