I have a separate credit card just for work expenses and I charge everything that I am allowed so I use this as my double check. I also made a very simple spreadsheet.
Days of the week across the top and expense items down the side. My down the side are in the order I would use them.
Airport Parking
Taxi - in town
Taxi - out of town
Tips
Breakfast
Lunch
Dinner
Lodging
Rental car
Tolls
The matrix makes it easy for me to remember everything and I can also quickly see if I forgot to account for something.