Originally Posted by Palal

It's generally easier to reprogram all your numbers in your phone (including the US numbers) to include a + before the country code (1 for the US). This way you can dial any number in your phone from anywhere in the world.

All my phone numbers are now:
+[country code][phone number]
So, for the US it's :
+14151234567
For, say, Czech Republic it would be
+420[phone]
Germany:
+49[area code+phone]

Makes things very easy without having to remember local prefixes for dialing international or local numbers. GSM is smart enough to determine what to dial.

Originally Posted by xyzzy

If you have a GSM phone it's easy once you find out how to dial a +. (often you hold the zero down to dial it). Dial +<country_code><city/area_code><number>. You should generally leave off any leading zero in the city code.

So, if you're in the UK and you see a phone number that looks like this: 0845 123 4567 dial this: +448451234567