Asteroids range from bus-sized to airplane-sized

The smallest asteroid is about bus-sized (25 feet), the next is a bit bigger (34 feet), and the largest stretches as long as an airplane (230 feet).
They're pretty faint, so if you want to spot them yourself, you'd need a telescope.

NASA's NEO Surveyor mission will help find more near-Earth objects

Scientists use stellar occultations (when an asteroid passes in front of a star) to pinpoint their paths accurately. This technique has been used to track other asteroids over multiple occultation events.
Looking ahead, NASA's NEO Surveyor mission (timeline not stated in the source) is intended to help find more near-Earth objects.