If you like to shoot on Auto - then continue to do so, but after taking your night shot review it in the viewer - if it is overexposed, then simply use the exposure compensation buttonand command wheel to dial in a stop of underexposure.
Say you get your shot and it comes out too light when you have a quick look - don't panic, just dial in "-1" in the exp comp (read manual!) on my camera the exp com button is right next to the shutter release. Turn the command wheel until the top LCD shows -1EV. Take another shot - this time it will be a bit darker. Still not enough? A bit more exp comp, so tweek it to "-1.3" and shoot again - delete your first washed out pic to save space on the card. You now have two to compare. One at -1 and one at -1.3. Each time you improve the exposre, you can delete the poorer one. Saves a huge amount of computer time back home!
If the opposite is true and your picture is too dark, simply set the exposure compensation to + side, so you would start at +1EV, then try +1.3....and so on until you got a good exposure. To set the exposure comp only takes as long as pressing the shutter button when you are used ot using it. Practise before you go on anything - buses in the street outside if you like! It doesn't matter, it is only so you can see what happens when you use the exp comp facility - quick and eas and just like using M mode! You will soon be able to guess the amount of exp comp to use as your starting point pretty accurately according to the scene - experience helps but it is still just an educated guess. The more you do it, the better your guess becomes!
