Final answer:
Remain calm, gradually reduce speed without abrupt braking, steer steadily, and pull over safely before calling for roadside assistance or changing the tire.
Step-by-step explanation:
If you get a flat tire while driving on a two-lane road, the best thing to do is to remain calm and do not brake harshly or suddenly. Instead, gradually reduce speed while keeping the steering wheel steady to maintain control of the vehicle. Look for a safe, level place to come to a stop, such as a widened shoulder or a parking lot. If you're unable to change the tire yourself, it's best to call for roadside assistance.