If you plan until staying out till the end of the night (2.30) you can avoid the taxi rank queues by asking your hotel or hostel or host to book a taxi in advance (even half and hour to an hour before you want to leave). There are several different cab companies - National Radio Cabs ( biggest and most reliable), Citi Cabs, Blue Cabs - etc. They charge a couple of euro extra but worth it if you dont fancy waiting an hour at the rank.
There are also a number of hackney companies that only pick up on reservation (they dont have a taxi sign, rather a very small yellow plaque on the cars bumper).
If you're out late-night in Dublin, keep in mind the ONLY place you can get a taxi is down by Trinity UCD. This phenomenally ridiculous situation can mean an ungodly wait for a cab, which is not so pleasant when one had counted on being somewhere (like, say, a hotel or bed and breakfast) any time near the time you were ready to go home. I'm curious as to why this is. Nonetheless, plan on it taking forever to get home after bus service stops. On the positive side, it is an opportunity to interact with Dubliners who are in the same position of waiting.
Most of the other tips are a little dated as any taximan in Dublin will complain about for the duration of the journey. There was a deregulation of taxi licences in the last few years and now there's an abundance of them in the city. I've been told there are more taxis in Dublin than New York.
Ranks aren't as popular nowadays with most people choosing to flag a taxi on the street. Worst thing is the traffic jams they cause at 4am are worse than rush hour on some streets!
Fares from the airport to the city should never be more than 25 euro,
If you are going Southside make sure that the driver does not use the M50 motorway as it is 18 miles longer that way,
Always go thru the city as the Taxis can use the bus lanes,
IF you are heading say to Jury's in Ballsbridge the fare should be about 25 euro tops
same for the Burlinton and Four seasons,
Always get a printed receipt and tell the driver that when you get in as he will have to use the Meter , The receipt will have all his details so if there is a problem you can report him,
You should never have to use the M50 for any fare, Remember Dublin has a huge amount of African taxi drivers who see tourist as easy prey , So be careful out there
Getting a taxi in Dublin city centre is easy. However, if you plan a trip to the beautiful village Dalkey (just outside Dublin, home to the rich & famous), do not ever use Dalkey Taxi Service.
Their staff that is not only rude, but also incapable of finding a street with more than 10 shops and 3 bus stops in the middle of Dun Laoghaire (between Dalkey and Dublin). I have never been treated in such an unprofessional manner. They kept telling me the street where I live did not exist. I recommend Dalkey Taxi Service hire friendlier staff that is capable of reading road maps or else they will be out of business soon enough. Very disappointing.