Worried that you'll spend hours getting through the U.S. border when you arrive with your nonimmigrant (temporary) visa or on the Visa Waiver Program? U.S. Customs and Border Protection (CBP) is trying to speed the process up, most recently by making a change to its I-94 website. Travelers will now be able to apply and pay for their I-94 document (an entry record that also shows your required departure date) online, within the week BEFORE you present yourself at a U.S. border point.
This system lets you avoid time you would otherwise have to spend at the border providing your name and other biographic details (date of birth and country of citizenship), passport details, visa details, and your visa petition or Student and Exchange Visitor Program (SEVIS) number (if applicable).
You will receive what's called a "provisional I-94" after submitting your online application and paying the $6 fee.
This doesn't get you a final I-94, however. To obtain that, you need to actually show up at the U.S. land port of entry within seven days of your application and request admission to the United States. You may also need to submit biometrics (fingerprints) and will likely be interviewed by a CBP officer, who will also check to see that you have your other required documents (visa, evidence of residence and employment, and a travel itinerary).
If you fail to show up within the seven days, your provisional I-94 will expire and you won't get a refund.
To apply for your I-94 online, go to the CBP's website at https://i94.cbp.dhs.gov.
Note that use of this system is not possible (or necessary) for people arriving by air or by sea.