I'm using the standard deduction for my federal taxes, but I want to itemize my state taxes. How do I just itemize state deductions on TurboTax?

[DoninGA]

 It depends on your state tax code.  Some states allow itemized deductions on a state return when the standard deduction was taken on the federal return.

Other states only allow itemized deductions if the itemized deductions were taken on the federal tax return.

[SteamTrain]

...And if yoru state does allow you to do Federal as Std Ded, and State-itemized, you will need to enter virtually all your "potential" deductions in the Federal section.....then they get transferred to the state automatically. 

Things like Mortgage interest, and Charity donations, out-of-pocked Medical expenses...etc, are entered in the Federal section.  If there are some special state deductions  (like 529 account contributions), then those special ones are handled during the state interview.

[xmasbaby0]

As explained already in this thread, you can enter itemized deductions into your federal return software and they will flow to your state return.  Even if the itemized deductions do not help you on your federal return, they could help on your state return in the following states:

Alabama, Arizona, Arkansas, California, Delaware, Hawaii, Idaho, Iowa, Kentucky, Minnesota, Mississippi, Montana, New York, North Carolina, Oregon, and Wisconsin.