by Julieanne Kost
• Holding the Option (Mac) / Alt (Win) key while dragging with the Marquee tools creates a selection from the center.
• Holding the Shift key will constrain the Marquee to a square or circle.
• After starting to draw a selection, holding the spacebar (while still holding the mouse down) allows the repositioning of the origin of the selection. Releasing the spacebar (while still holding the mouse down) allows continuation of drawing of the selection.