The Pen Tool Review

http://vector.tutsplus.com/tutorials/tools-tips/illustrators-pen-tool-the-comprehensive-guide/

1. Functions

Pen Tool (P)

Click on artboard to create paths with straight segments, click and drag to create paths with Bezier curves.

Add Anchor Point Tool (+)

Click on a path segment to add anchor points.

Delete Anchor Point Tool (-)

Click on anchor point to remove from path.

Convert Anchor Point (Shift + C)

Click on an anchor point and drag to create bezier handles where there were none, click on an anchor point with handles to a remove them.

Scissors Tool (C)

Not part of the Pen Tool group, but definitely associated with it. Click on a path segment to divide into two paths.

2. Keyboard Shortcuts

Select Pen Tool (P)
Select Add Anchor Point Tool (+)
Select Delete Anchor Point Tool (-)
Select Convert Anchor Point Tool (Shift + C)
Select Scissors Tool (C)

3. The Cursors

The Pen Tool takes on different forms depending on what you’re doing when you’re using it. Each one intuitively makes you aware of the action you are about to perform.

(Caps Lock to toggle between pointer and cross hair)

Prepared to begin path
Whilst midway through creating or editing a path
When mouse is pressed
When hovered over path section; to add an anchor point to path
When hovered over anchor point; to remove anchor point from path
When hovered over begin point of path; to close path
When hovered over endpoint of existing path; to continue path
When hovered over existing anchor point

4. Secondary Mouse Controls (With Path Selected)

Pen Tool hover over anchor point: changes to Delete Anchor Point Tool
Pen Tool hover over path segment: changes to Add Anchor Point Tool
Pen Tool hover over end anchor point: changes to Convert Anchor Point Tool

5. Keyboard Controls

Hold Shift to constrain movements to 45°, 90°, 135° or 180° whilst creating or editing anchor points and handles.
Select anchor point with Direct Selection Tool (A) and click Delete. Anchor and adjoining path segments are deleted leaving two paths.
Pen Tool + Option (Alt): changes to Convert Anchor Point Tool.
Pen Tool hover over bezier handle + Command (Control): allows editing of bezier curve.
Pen Tool + Option (Alt) whilst creating bezier curve: splits curve (unhinges handles).
Pen Tool hover over bezier handle + Option (Alt): splits curve (unhinges handles).
Scissors Tool (C) + Option (Alt): changes to Add anchor point tool.
Add Anchor Point Tool + Option (Alt): changes to Delete Anchor Point Tool.
Delete Anchor Point Tool + Option (Alt): changes to Add Anchor Point Tool.

6. Preferences

You can access the preferences which influence the Pen Tool (P) and other related tools by going toIllustrator > Preferences > Selection & Anchor Display.