Nightlife in Limerick is fairly limited.
Pubs I would recommend are:
Dress Code: Smart Casual. Make an effort on Saturday nights.
The Locke Bar is a really nice pub at the Abbey River, next to the Potatoe Market and the city hall. You can sit either insides or outsides (only in summer of course). Outsides you'll miss the live Irish music though: everyone who can play an instrument can go there and join in with all the other musicians. By the way, it was in this pub where I had my very first Guinness!
Au Bar - Thomas St
Clohessys - corner of Mallow st
Dolans - Dock rd (not v central though)
Nancy Blakes - Denmark st
The Old Quarter - Ellen St (not student friendly, so dress up and put lots of make-up on)
The Locke Bar - Georges Quay. One of Limerick's oldest pubs
Docs - studenty pub/club. Used to be cool and Indie. Now its' techno and rave and I wont go there anymore. But if you like that kind of music then you won't mind. It's got a beergarden, lots of UL students trying to pick up teenagers ;) and strict bouncers
Blend in with the locals with a spot of beermat dancing :)
Dress Code: Nothing out of the ordinary. If you want to go to a classy bar, wear something appropriate.
No matter where you go in Limerick, always take some ID with you, as there are a lot of underage pubbers and clubbers out there. I was one of them, so I should know ;)
To be honest Limerick is absolutely brutal to go out in.
There are a few clubs The Market, Docs, The Globe, The Gallery, The Voodoo Rooms (good on occasions)...
Best nites are Nu Killa Beatz (drum n bass) in the Doghouse if you'Re into that kind of thing, and then Soul Clinic in the Dolans Warehouse after.
Always a nice happy friendly crowd at the Doghouse and Dolans.
Dress Code: Totally casual.