Dublin, like any city, has a seamy underbelly into which the unwary visitor should not stray. This is not just true geographically, but also conversationally - either way straying from the recommended path can have potentially dire consequences.
Pockets of real poverty and deprivation exist quite close to the city centre and it is not advised to wander round these places without knowing full well what you might be getting into. These include areas off O'Connell Street, the Sheriff Street area near Connolly Station, some areas near the Guinness Brewery and various other pockets that any Garda will readily identify for you if you ask. I must stress that there are many decent people living in these places (to me they are some of the last bastions of the "real Dub" wthout which the city is all the poorer) and that the dangerous element living there represent a tiny minority. Still, a tiny minority kicking the crap out of you still bloody hurts so you'd be mad to carry expensive gear or clothes that mark you out as an obvious "outsider" when wandering around there!
Conversationally the city is also well mined with booby traps. Subjects to avoid change with events but at the moment try to steer clear of the following if amongst strangers, or at least be prepared for "lively" debate!:
Anything to do with Irish history if you have an English accent.
Anything to do with the Middle East if you have an American accent.
Gay rights unless you're pretty thick skinned - Dubliners can be quite blunt.
Ethnicity and racism - Dublin is on the verge of discovering just how racist it is and the state of denial that many Dubliners are in can cause them to be quite "vociferous".
One old taboo - the Catholic religion - has recently lost that status due to scandals so the challenge now should you criticise it is to find someone to disagree with you!
Fondest memory: Having said all that, life is no fun unless you break some rules now and again. A visit to Dublin can be memorable as much for the lively banter as for the sights it offers, at least to those who negotiate the minefield described above successfully (or plough through it with gay abandon!).
One piece of advice holds true above all others however, regardless of whether you broach these taboos or not: - Never sound like you know more on a subject than the stranger to whom you speak, even if you can produce written qualifications from your pocket to back up your authority in the matter! The typical Dub's expertise has been acquired through his or her own "private research", not from listening to others, and he or she is not about to change his or her study method now!
In Ireland, we pay a government levy of 15c (at present) on plastic bags.
I work in retail and get a lot of complaints from customers regarding this scandalous method of ripping off tourists.
You're right, that 15c could be better spent on a car loan, mortgage or extra weeks stay in the country, but, unfortunately, our greedy government wish to protect the environment- imagine such an abbhoration!
So, if grocery shopping, please remember to either bring your own bag or be prepared to re-mortgage your home to get the extra cash for a carrier bag.
Edit: bags cost 22c now!
This is for the UK visitor who is thinking of coming to Dublin for a stag/hen party. It's probably best if you don't come to Dublin for it, go to another Irish city. Here is why.
If you're booking accomodation, DO NOT tell them you're a UK stag/hen party because all of a sudden, it's "Oh dear, fancy that, we're fully booked". They don't have a good rep here, I'm sorry to say.
Stag/Hen-friendly places would be either Club M in Temple Bar or Break for the Border, near Stephens Green or Trinity Arch on Dame St.
A lot of bars in Dublin City Centre will not let stag/hen parties in at all, so hide the plastic willies and boobies if you can.
Some pubs in Temple Bar even have signs up saying "No Stags or Hen parties", so you really have to be on your best behaviour if you want to go somewhere decent, otherwise you'll just end up in crap cheesy nightclubs with a load of other UK stags and hens.
If anyone in the party shows signs of "getting merry", they WILL be asked to leave - I have seen this happen a couple of times in bars (e.g. The Bank in Dame St).
There are loads of other things to do in Dublin, get out of the English colony that is Temple Bar and see the *real* character of the city :-)
I reserve a hatred for one place on this planet and that place is Dublin. Tell me people whats so mystical and special about a city over run with heroin addiction and petty crime. Home to the stag do of many an uncultured idiot. Which in turn has made sure that the cost of living is nearly beyond the means of the average resident. European Union membership has brought jobs and new roads and unbeknown to most 'tourists' some of these roads lead out of Dublin. Please do your token rip off tours and then make time to see Ireland( while its still there). Examples can be found mainly on the west coast, Kerry, Galway, Clare etc.
So unless of course spending a fortune in an open sewer is what passes as a holiday please avoid this hell on earth.
Fondest memory: Being mugged twice, once at the bus station and once at Heuston train station. Oh and lets not forget the begging junkies and the extremely irritating taxi drivers. I forgot to mention that lovely fresh smell from the Liffey.