I am an Indian citizen studying in the US on an F-1 Visa. I am in the second year of my graduate degree and will start working (off-campus) part-time under the CPT program. I am not sure which tax form to fill as a Non Resident Alien - Form 8233 or W-8BEN or W-4. Could you please help?

You will file nonresident tax return Form 1040NR or 1040NR-EZ with form 8843. Your U.S. Tax Return: U.S. Tax Filing Requirements for Non-Residents (http://taxipay.blogspot.com/2008/03/us-tax-filing-requirements-for-non.html)