There are lots of ways you can deduct mileage. To do so though, you need to be able to substantiate that deduction.
How do you do it?
A mileage log for each vehicle including the Date, Destination, Business Purpose, Starting & Stopping Odometer Readings and Miles for that trip.
Also keep track of business vs. personal miles for each vehicle.
Business 54 cents
Medical 19 cents
Moving 19 cents
Charitable 14 cents