General guidelines are:
red at room temperature
white slightly chilled

I make it dependent on the individual wine and the situation I need it for. Any time one chilles a wine, refreshment is traded for flavor, since chilling captures flavor.
Heavy reds are certainly best at room temperature. Light reds can also be slightly chilled (I am thinking of light Pinot Noir or Gamay).

Whites I generally chill a little bit. It adds refreshment to it. The better and more intense the wine, the less chilling it needs, especially when there is acidity that makes it refreshing. The more one chills the wine the less of the flavor will be released as one tastes the wine. With a good wine, some of the flavor is lost, with a not so good wine the bad flavors are hidden when you chill it really well. As usual it depends what you want to achieve. Whatever pleases you is the right thing to do!