The government has an excellent publication covering everything about I-9s that all employers should know about. Here’s what it covers:

Obtaining Forms and Updates

Part One — Why Employers Must Verify Employment Authorization and Identity of New Employees
Part Two — Completing Form I-9
Part Four — Unlawful Discrimination and Penalties for Prohibited Practices=
Part Five — Instructions for Recruiters and Referrers for a Fee
Part Six — E-Verify: The Web-based Verification Companion to Form I-9
Part Seven — Some Questions You May Have About Form I-9

Click here to access the handbook.