Here's a link to what's required in Douglas County. Call your local building department, they'll give you a good idea of what the proper method is for your area.
Also, if you're placing footings within 5 feet of an existing structure, the footings have to go down at least to the depth of the existing footing. Otherwise it looks like 36 inches is normal (at least for Douglas County). That's typical of NJ as well.
Also, it looks like they pulled a lot of the details right out of the AWC's Prescriptive Residential Deck Construction Guide, with a couple modifications. Here's a link to the original PRDCG: