The standard American telephone number is ten digits, such as 555-555-1234.  The first three digits are the "area code," which sometimes must be dialed even when making a local call. If you are calling a number outside the originating area code, you may need to dial "1" before the ten-digit number if using a residential landline phone. Hotel and business phone systems have their own specific dialing requirements.

Many numbers are reserved or are of note. 911 is the number that can be dialed for free from any phone (even a pay phone) to obtain assistance from emergency personnel. 411 is the number for directory assistance, though a charge will apply; 1-800-Free411 is the number for free directory assistance (though callers will listen to ads). Numbers begining with "800" (which now include 888 and 877, among others) are special area codes that are considered a local call from anywhere -- hotels may charge special connection fees, though. Any phone number that starts with 1-900- should be avoided, as those are to companies/establishments that charge a per-minute fee for speaking with them and may include objectionable content.

Cell phone coverage is generally good in populated areas but, unlike some parts of the world, different carriers have exclusive systems and areas. This means that your service in one area may be terrible, but your friend's phone with a different service provider would work great. In addition, many subways and buildings have mediocre or non-existent coverage. GSM mobile telephones in the United States generally work at different frequencies than in other countries, with 1900 MHz being the most common. Recently 850 MHz has been used in cell phones, particularly on the Cingular Network. You may need a tri- or quad-band telephone to work in the USA. Check with your cellular provider regarding equipment/service compatibility before traveling.

Calling cards are easily obtained from most convenience stores. Some hotels, vending machines, and most every supermarket also sell these easy-to-use calling cards. Since most hotels have very steep fees for phone use, a calling card can save you a lot of money. Be aware that hotels may charge fees for local calls and toll-free calls as well as long distance. There should be a card in your hotel room that outlines all the phone fees. If not, contact the front desk for information before making a call.