Is there a better day or time to book a car rental?

The busiest days at my branch are Friday and Monday (weekend renters and returns respectively), and the weekends before major holidays. If you make a reservation, however, you should be able to get a car regardless of how busy the branch is, since they should be expecting you and should have the type of car you requested.

If you want to have more selection, or you want to do a walk-in, try the middle of the week (Tuesday, Wednesday, Thursday), and don't go to the airport location.