You each file single. One takes head of household if there are kids. Decide how the deductions should be taken for real estate taxes. You had a lawyer. You are best served by discussing this with your lawyer.
Single and perhaps head of household. Talk to an accountant.
This communication does not create an attorney-client relationship. This communication constitutes general legal advice directed to the public at large. Consult an attorney regarding the facts specific to your case in your jurisdiction.
If your were divorced in June of 2012, your marital status at the end of the year should control. It would appear that you'd file either "single" or "single head of household" as the case might be. You are no longer married and would not file jointly.