Twilight is the one of the most magical times of the day, and with a little planning and patience you can capture some of the mystique.  The camera continues to see and record colors long after our eyes stop seeing it.  Resist the urge to over process in post production.   You want only a hint of light,  just enough to recognize the scene,  but you certainly want to keep the stars bright in your photo. 

Just because the sun sets, it doesn’t mean you have to put your camera to bed.