The Polygonal Lasso tool lets you create selections with straight-line segments so that you can create complex geometric areas such as starbursts and objects in perspective. It does not let you create curved segments, however, so make sure that the area you want to select is suited for this tool.
Open the File
Choose File, Open and select the desired file.
Select the Polygonal Lasso Tool
Click and hold on the Lasso tool in the toolbox and drag to select the Polygonal Lasso tool from the pop-out menu that appears. Note that the selected tool now appears on the toolbox button and in the Options bar at the top of the screen.
Click the First Point
Move the pointer onto the image and click to place the first anchor point. After placing the first point, notice that a straight line extends between the anchor point and the mouse pointer. This line indicates the selection line that will be created when you click to place another anchor point.
Add Other Points as Needed
Click once at each location on the image, and place as many anchor points as necessary to surround the area you're selecting.
Close the Selection
To define an enclosed area, you can close the selection shape by clicking back on the starting anchor point. Alternatively, you can double-click or +click (Mac users) or Ctrl+click (Windows users) to connect the current point to the starting point. When you do this, the selection process is complete.
Using the Shift Key for Right Angles
Press and hold the Shift key to constrain the line segments you draw with the Polygonal Lasso tool to increments of 45-degree angles.
For Organic Selections
Select the Lasso tool instead of the Polygonal Lasso tool to draw freeform shape selections. You can switch to the Lasso tool from the Polygonal Lasso tool on-the-fly by pressing and holding the Option key (Mac users) or Alt key (Windows users) as you drag freeform shapes. Release the Option/Alt key to go back to dragging straight lines.
A Geometric Alternative
If you want a little help with geometric selections, try the Magnetic Lasso tool, found in the pop-out menu of the Lasso tool in the toolbox. Click and drag the tool around the selection area, and the selection snaps to the nearest contrast edge. The settings in the Options bar allow you to control the "snap-to" qualities of the tool, which you can adjust as needed.