This is always a very important thing many people do not realize what they need to record when tracking business mileage.
1) Date - Be sure to record the date of business travel
2) Destination- City, Town or area
3) Business Purpose- What is the purpose of this travel
4) Odometer Readings - Start and Stop
5) Total Mileage of this Trip- Total the mileage traveled for this trip
Be sure this is neatly tracked in a journal of choice ie Notebook, journal book
Also there are different apps that can be used that follow IRS Business Mileage log guidelines that can also be used and printed.
Be sure to keep these records each year in case it ever comes into question by the IRS.
Also January 1st be sure to record your odometer reading for the start of the year and also Dec 31st record your year end odometer reading.