Stay after sunset! 

A quick tip on photographing sunsets: When the sun goes down, don't be so quick to put away your camera! A partly cloudy sky can still be lit up for about 20-30 minutes after sunset. The colors one can get are pretty wild, especially when shooting HDR.

Music by _ghost at http://ccmixter.org/people/_ghost, the aptly titled "Sol, Solar, Solaris".