Go to a beer review website and look up whatever beer you're trying. Being in NZ, you probably won't have the selection people in the US have, but you'll probably be able to find several beers that have lots of reviews. Then while you're drinking the beer, read what the other reviewers are tasting and see if you can taste it too. Many times you'll pick up on a flavor that you just can't quite describe, then you'll read someone else's description and they'll mention that there's the faintest hint of mango. Then you'll realize THAT'S what it is you tasted. Next time you taste it, you'll remember.
EDIT: beeradvocate.com is a good place to start.