If you're heading into seemingly-hostile territory or simply want to survey the area around you for enemies you might not yet see, try hitting the VATS button over and over again as you make your character turn around, searching all angles. Doing so will alert you to any enemies you may not yet see by zooming in on them in VATS mode. You'll realistically be unable to do damage to your foes from such a distance, but it's a good way to spot foes before they spot you so you know what you're getting yourself into before the crap hits the fan.