International Direct Dialing codes for Phones.

There are two ways to Dial a Phone in another country.

1. Operator Assisted dialing,which you contact your operator and ask him to ask them to connect the
    desired number to your phone.
2. International Direct Dialing,which you can dial the land or mobile phone directly from your phone if your
    service provider allow you to do so.For this you must knoe the country ,City codes of the phone you want
    to call.
When you are calling,off peak hours will give you more talking time for your money.Rain and hot sun may affect your phone call by giving you unnecessary noises.
And if you are in a new country,Vist the local post office and get the latest dialing information from them,as most of the countries are upgrading their net works every year.Also if you are calling from a city to city,it's better to ask them regarding the way of Calling another city numbers.
Here is a sample Number for Calling UK
0044 or +44 Country Code
Next followed by City code number.
+44 2xxxxxxxx2

Here are some usefull information.
International Direct Dialing Code Numbers. (IDD)