If you are married and file a separate return, you will usually pay more tax than if you use another filing status for which you qualify. Also, if you file a separate return, you cannot take the student loan intrest deduction, the education credits, or the earned income credit.
You also cannot take the standard deduction if your spouse itemizes deductions.
Generally you report only your own income, exemptions, deductions, and credits. Different rules apply to people in community property states. See Form 1040 instructions or Pub. 555 for more details.