00 1 from a landline or +1 from a GSM mobile phone, followed by the area code and number.
Dial 00 353 and then the landline with its area code and leaving out the first zero.
All Irish (Republic) mobile phone numbers start with 08 and the following digit denotes the network operator the number was originally registered with. Example 08 5(meteor network) 2993856
Just as you would call an English landline.
To call a UK mobile from a UK landline, you always just dial the UK mobile number, exactly the same way you do when it is in the UK. The network will find the mobile automatically, and the mobile user will pay any applicable surcharges for international roaming.
To call Spain from any GSM mobile, anywhere in the world, dial +34 and then the 9-digit Spanish number (landline or mobile).
To phone anywhere in the UK from Ireland, replace the trunk prefix 0 at the beginning of the UK number with 00 44, or +44 from a GSM mobile. There is one special code. To call a landline in Northern Ireland from the Republic of Ireland, you can dial 048 instead of 00 44 28, followed by the 8-digit local number.
You would ring it in the normal way, as if it was still in Ireland. You can add 00 353 at the start and then drop the first 0 before the 8 and then the rest of the number as normal.
from Ireland dial: 0044(united kingdom) 28(northern Ireland) xx(local area) xxxxxx(phone number) ta-da.
On a GSM mobile (from any country, in any country), just replace the trunk prefix 0 of the UK number (landline, mobile, or other) with country code +44, including the plus sign. For example, the fictitious number 0151 496-0123 becomes +441514960123. From a landline, or from a non-GSM mobile, replace the plus sign with 00.
From a GSM mobile phone, dial +1 310 and the 7-digit mobile number. From a landline, dial 0011 1 310 and the 7-digit mobile number.
You dial the normal number. The phone network will handling routeing the call to wherever in the world the mobile currently is.