Can I deduct my mileage if I donate items to goodwill?

I do not believe so.  Check out IRS pub. 969.

Yes

yes you can

Is this mileage form home to organization only or is this mileage for a round-trip?

round trip

Mileage to drop off donations is deductable -  Intuit (Turbo Tax) on line It's Deductable has this covered.

That assumes the donation drop off is the sole purpose of the trip. If you stop at the grocery store , then you can't deduct it.

YES, definitely use It's Deductible and be sure to imput the miles and it will calculate the deduction for you.

Yes.

But, unfortunately, the charitable contribution rate is only $.14/mile.  The business rate doesn't apply.

Also be sure that was the only thing the trip was for. E.g., if you stop at the grocery store on the same trip, the mileage isn't deductible.