In NY state I pay property tax and School tax on my home. Do I include the combined amount under "(Real Estate) Taxes"or is there a separate spot to enter the school tax?

Combine them, they are both taxes on your real property.

However, you can only deduct general taxes that apply to all homeowners in your area, you can't deduct special charges that are for improvements, services, or for benefits that you have that other properties don't.  For example, if all the homes on your street are charged $50 for streetlights, which fee is not charged to people who don't have street lights, then it's not a deductible property tax.  Or if all the houses on your street have a special assessment for a sewer upgrade.  Or if there is a charge for trash service that is listed separately, that's not deductible.  On the other hand, if there is a charge of $50/year for fire and ambulance service, and that is charged the same to every home, then it's deductible because it's paying for a general community benefit instead of a specific benefit to you.  

You should review your detailed bill from the county to make sure everything on it is an allowable deduction.