Photoshop offers two Marquee tools (Rectangular or Elliptical) for making simple geometric selections. They’re easy to use.

Click hold and drag to define a selection.

Hold the Option key to draw from the center of the shape.

Hold the Shift key to constrain the shape to a perfect square or circle.

You might question how often you’ll use simple geometric selections, particularly in complex photographs, but you’ll be surprised. They’re excellent for quickly selecting large areas of a canvas, which can be further refined with any of the other selection tools. They’re extremely useful if you feather them heavily; targeting the center of an area then fading off gradually to create vignetting effects, either for the entire image frame or a small portion within it.

Read more about Selections & Masks.
Learn more in my digital photography and digital printing workshops.