The basics of the first-time buyer tax credit before they were revised in the American Recovery and Reinvestment Act.
If you bought your first home last year after April 9, 2009 you are eligible for the lesser of $7500 or 10% of your purchase price in the form of a tax "credit."
You can not have owned a home in the three years previous to the purchase. The credit reduces the tax liability, and if there is a balance after taxes are collected, it is paid out as a refund to the home buyer. The adjusted gross annual income to receive the full credit can be no more than $75,000 for individual, $150,000 for joint filing, and there are reduced credits for first-time home buyers above those income levels.
Read everything about getting the tax credit at Philadelphia and Bucks County Real Estate Blog