If you’re riding at night, check if the lights are working by holding your hands under the basket and rear wheel. The lights turn on automatically, and it should be very clear that the front light is working as it creates a light affect in the basket.
Make sure that the seat is properly adjusted to the height that is most comfortable for you to ride.
Ensure that the seat is firmly clamped and not loose in any way.
While at a low speed, test that both brakes are working appropriately.