next Step 1: Draw a selection with the polygonal lasso tool  
 
Step 1: Draw a selection
Choose the Polygonal Lasso tool, and draw a selection as follows:
· Click to start the selection
· Move your mouse to where you want the first straight segment to end, and click.
· Continue clicking to set endpoints for subsequent segments.
· To close the selection, either double-click or move to the starting point.

You can now automatically adjust the selection as shown in step 2.