Force.com IDE Developer Guide

Getting Started with the Force.com IDE
Developing with the Force.com IDE
Testing Code with the Force.com IDE
Deploying Code with the Force.com IDE
Getting Started with the Apex Debugger
Summary of Getting Started with the Apex Debugger
Set Up the Apex Debugger
Contact Salesforce to Enable the Apex Debugger
Install or Update the Force.com IDE Plug-In for Eclipse
Set Up a Permission Set
Create a Project
Test Your Debugger Setup
Whitelist Users and Request Types
Explore a Simple Debugging Puzzle
Manage Debugging Sessions
Apex Debugger Limits and Considerations
Apex Debugger Troubleshooting
Force.com IDE Release Notes
Useful References
PDF

Contact Salesforce to Enable the Apex Debugger

Some services and subscriptions include this feature for an extra cost. For pricing details, contact your Salesforce account executive.