A detail that surprises a lot of first-time renters.
In much of the world outside North America, manual transmission is still the default rental option, and automatic vehicles often come at a premium or need to be requested well in advance. Booking early matters more for automatic transmission availability than for most other rental preferences.
If you're not comfortable driving manual, confirm your automatic reservation is guaranteed rather than just requested, since some smaller agencies can't always fulfill it on short notice.