How to call from one Country to another.
In order to make a direct international phone call from country to country, the following things need to be known.

First thing is the International Direct Dialing prefix for the country you are calling from.
You can find this in the third column of the International Dialing Codes page.
For instance, the International Direct Dialing prefix to call from United States to any other country is 001. In numerous other countries, the International Direct Dialing prefix is 00. Other countries have different prefixes, or may offer more than one which depends on the carrier and type of your calling service. It is imperative that the International Direct Dialing prefix for the country you are calling from is correct. This code will be the first numbers that your dial to make a call as shown below.

The next set of numbers is The Country Code of the country you are calling to.
This is available in the second column on the International Dialing Codes page.
Every country has a specific distinct code, though in some cases it can be shared with other partner countries. For instance, United States, Canada, and much of the Caribbean and even Guam use the country code of 1. This code is dialed right after the International Direct Dialing prefix and before the area/city code and phone number, as shown below.

The area/city code for the number you are dialing.
To find out this code, click on country's hyperlink on the International Dialing Codes page.
There are some smaller countries that do not use area/city codes, but for the most part, larger ones may have hundreds of them. Due to the enormous population growth, most nations� area/city codes are changed and added very frequently. If you look at the International Dialing Codes page and the country�s name is highlighted as a hyperlink, this means that there may be a list of area/city codes or other information that might help you complete your call. This is the most difficult information to keep up to date. Therefore, some listings might be incomplete or outdated. While some countries don't use city/area codes, if the country is not listed on that page, it could be that we simple do not have that we don't have the code.

i.e. Calling from USA to Tripoli, Greece.
Look up and dial:

International prefix for USA	Country Code for Greece	Area Code for Tripoli	Phone number you are calling
001	30	271	XXX-XXXX

Note: In most hotels, you will need to dial 9, 0 or perhaps another number to obtain an outside line).