The basic thing to remember in Ireland is you need to dial “0″ first when placing a call (the “0″ is usually included before any phone number when written).
Phone services (emergency, information, etc) are the exception to this rule – no zero necessary.
To dial internationally, you’ll need to dial “00″ and then the country code and number.
Emergency services, dial 999 (no pre-zero).
Domestic operator is 10 (no pre-zero).
International operator is 114 (no pre-zero).
Directory Enquiry services (no pre-zeros here either) are provided by a number of independent companies. Eircom’s 11811 is the national service. Conduit’s 11850 is a business listing and Vodafone’s 11844 is for mobile numbers. All of these charge per call (usually less than €2) and will usually text the number to your mobile phone as part of the service.
Ireland’s phone listings are currently undergoing a complete change as area codes are being introduced nationwide. With the exception of large metropolitan areas (like Dublin, which is 01, for example) all areas former 3-digit extensions are being replaced with 4 digits.
To dial Northern Ireland the safest way is to dial as if you’re calling internationally to England (yes, remember Northern Ireland is a different country entirely than the Republic of Ireland). Dial 00 44 28 followed by the number.