There are many things that you need to know to get ready specifically for any criterium race day to guarantee optimum performance.
The most important thing you need to know the day of your criterium cycling race is the start time because based on this you can time when to eat before the race, when to warm-up and when to start getting close to the start/finish line to get a good race start position.
When getting ready for a criterium race day you need to eat 2-3 hours before the race so that you can race on an empty stomach. This is better because your diaphragm has more room to function during the respiration process, allowing you to fill your lungs with oxygen to 100% capacity, helping your heart to send more oxygenated blood to your muscles while racing. Also, racing on an empty stomach allows you to send more oxygenated blood to your legs rather than to the digestion process of your food.
Another important thing to time is your warm-up before the race. You need to warm-up for at least 30-45 minutes on your bike trainer or bike roller until 20 minutes before your start time so this way you get your circulatory system dilated in preparation for the high intensity that a criterium demands. Your arteries that deliver blood to your legs need to be stretched out to the maximum in order to match the high blood volume that the heart will start pumping to your legs once the race starts.
And last but not least, you need to start getting close to the start/finish line 10 minutes before the start time, so that when they call the riders to the start line to start the race, you can be one of the first riders to get a front position. This will allow you to ride in the front of the peloton at the beginning of the race, so you can be ready to join any breakaway that usually happens early on in technical criterium cycling races.