I log every time I walk out the door where and with who for what reason,

Annette, good question.

I keep a log as suggested my CPA. We use the standard mileage deduct. 

I pay my CPA to handle all my taxes.  I keep track of miles and work truck but usually he goes with the gas receipts I keep.  I have a business credit card in the PLLC name, I put everything work related on it, which helps. 

Document, document document...Vern said it well also

Keep great records.

Use separate business vehicles and keep track of mileage.

Annette Lawrence , Palm Harbor, FL 727-420-4041 

I depreciate my vehicle and do not take the standard deduction.

I keep a paper mileage log to prove to the IRS my business vehicle usage. They do ask the question on IRS Form 4562.

I do not use a 3rd party, I keep my mileage log on a clipboard in my car.

I keep a mileage log and give that to my cpa.

I don't have to, I drive a company car.

I have a mileage log, and I add it up for each month and the yearly total and give that to my tax lady. 

My wife handles all that thank goodness!

I personally do not do  it, I have a leased vehicle used only for Real Estate but if not the way Roy Kelley mentions is how I have heard it done. Keep track of the mileage.

When I have done my taxes, I use mileage and not actual expenses, It has asked for my starting and end mileage and how much was used for personal and much for business. I use Turbo Tax and it has made things farily easy todate.

If you do not use the standard mileage rate, you may be able to deduct your actual car expenses. Beginning Jan. 1, 2015, the standard mileage rates are: 57.5 cents per mile for business miles driven, up from 56 cents in 2014.

It might pay for you to keep a log.