Tapering is common practice. This consists of reduced mileage and calories but still a few anaerobic workouts. Similar to the belief in easy jogging the day after a marathon, it can be good to do light running or exercise, one or two days before a race, for mental and physical confidence.
Avoid experimenting with meaty, gassy, spicy or hard-to-digest foods. Stick to carbs (pasta!), veggies and some good fats and protein for a normal size meal. A lot of dairy generally doesn't sit well prior to racing.
The most obvious and important ritual is to hydrate as early as 48 hours before, mainly water plus electrolytes, to help prevent dehydration, cramping, and any heat-related conditions.
Double check race logistics, gear and transport. Finally, sleep early for 7+ hours but don't stress if you end up getting less...adrenaline and a little caffeine will make up for it!