If you're taking shots of sunsets without foreground subjects, or with foreground subjects that you want to be silhouetted, I don't think there's any such thing as a "correct" exposure. I find that metering off the sky usually gives quite pleasant results: because the photo is essentially underexposed, the sunset colours are very saturated and vibrant.
With subjects in the foreground, I'd use some fill-in flash. Meter off the sky to get the background (i.e. the sunset) exposed OK, and the flash will illuminate the foreground subjects. Remember your flash won't sync properly at anything faster than about 1/200, so the lens will need to be stopped down appropriately to slow down the shutter speed. Make sure your subjects are within range of the flash. Check the exposure on the LCD after you've taken a shot and adjust if ncesssary. And I'd suggest bracketing the exposures too - it doesn't cost anything with digital and increases the chance of getting a good shot.
Have fun.