by Julieanne Kost
The Marquee, Lasso, Magic Wand and Quick Selection tools all share some common shortcuts that can help you when making more complex selections (Instead of using the icons in the Options bar):
• Holding the Shift key and dragging with the tool will add to an existing selection.
• Holding the Option (Mac) / Alt (Win) and dragging with the tool will subtract from the original selection.
• Holding the Option (Mac) / Alt (Win) + Shift and dragging with the tool will produce the intersection of selections.
• After creating a selection, you can move a it by 1 pixel with the arrow keys. Add the Shift key to move in increments of 10 pixels.
• Holding the Shift key after beginning to move a selection or layer will constrain the movement to multiples of 45° (0°, 45°, 90° etc.).