A great site for nano tanks is
www.nano-reef.com , I use both nano-reef and the reef tank religously and can get most of my questions answered.
As far as advice? go slow as most others are telling you. Read everything you can find on marine tanks in general and than read everything you can on nanotanks. I have had great success with mine, in fact I have had more luck with my nanocube 12DX than with my 45 gallon. But if something goes wrong in your nano it will happen extremely fast, so you need to stay on top of it and monitor it constantly.
Train a reliable friend or family member in the care of your tank, the last thing you want is to go on vacation and come home to find your tank has crashed because your "caretaker" got drunk and had a party at your house and had party members dropping crap in the tank, true story... Luckily it did not happen to me.
Invest in a refractometer...
Get rid of the bioballs and sponge (nitrate traps)
learn the cycle
add your critters slowly
find a local
reef club and try to get your corals through them, chances are they are healthier and put no strain on the reef, plus if something bad does happen you can most likely get a frag of the colony from the member you got it from originally, oh and they are a LOT cheaper too.
most of all spend lots of time staring at your tank, not only do you learn what "normal" is for the tank but it will prevent heart attacks

they are so relaxing.