When Claiming Exemptions for Dependent or Spouse:
You generally must list on your individual income tax return the social security number (SSN) of any person for whom you claim an exemption. If your dependent or spouse does not have and is not eligible to get an SSN, you must list the ITIN instead of an SSN. You do not need an SSN or ITIN for a child who was born and died in the same tax year. Instead of an SSN or ITIN, attach a copy of the child's birth certificate and write Died on the appropriate exemption line of your tax return.
How Do I Get A TIN?
SSN
You will need to complete Form SS-5, Application for a Social Security Card (PDF). You also must submit evidence of your identity, age, and U.S. citizenship or lawful alien status. For more information please see the Social Security web site.
Form SS-5 is also available by calling 1-800-772-1213 or visiting your local Social Security office. These services are free.
http://www.irs.gov/businesses/small/international/article/0,,id=96696,00.html