Utilities - QAR500-700 (depends on season & usage)
Groceries - QAR800-1800 (depends on whether you are vegetarian or not & the brands you buy)
TV - around QAR300 a month (I think cheapest OSN package)
Car fuel - very cheap compared to USA, QAR200-300 should do it for internal Doha travel unless you get a gas guzzler and have lots of daily long trips around Qatar.
School fees - as per LostInQatar's post above.
Clothing and entertainment - Free charity bin & free walks in parks to Dynasty-like prices in Doha.
You do the math for your lifestyle.