The Marquee tool is extremely useful, but sometimes you need to select an irregular area that can't be done with plain rectangles or ellipses. In this case, you will want to use the Lasso tool. Click on the Lasso icon in the tool bar. Your cursor will look like the loop of a lasso. The dangling tip of the rope is the selection point.
Click and drag to encompass an area of your image. As soon as you let go of the mouse button, the final point will automatically connect itself in a straight line with the starting point to form a closed loop. This loop is your selection area.
You can use the Lasso tool to surround an object that you want to separate from the background, as in the picture (right). The Lasso tool also has a menu bar (below), similar to the menu for the Marquee tool.
Using the addition, subtraction, and overlap functions of the Lasso tool, you can alter and fine-tune your selection area, as in the picture (below).
As with the Marquee tool, the Lasso tool also has different types. You can see the choices by clicking and holding on the Lasso icon in the tool bar, as shown in the picture (below, right).
The second choice on the list, the Polygonal Lasso tool, allows you to create a selection area by clicking in various places on the image instead of dragging. Each place that you click forms a corner of a polygon. The corners are automatically connected by straight lines. You can close the loop of the polygon either by clicking on the starting point or by double clicking.
With the Magnetic Lasso tool, the computer assists you in placing the outline of the selection area. It uses clues such as differences in color or brightness to recognize the outline of the object you are trying to select, and the selection area is "magnetically attracted" to this outline. With this tool, you don't have to worry about having a steady or precise hand, because the computer does the work of remaining true to the outline on your behalf.
The drawback, however, is that if the outline of the object fades into the background, the computer can't tell the difference and the "magnetic" effect doesn't work properly. You may have to use the addition or subtraction properties to clean up the resulting selection area to your satisfaction.