To present the smallest possible target to the enemy when firing, you should:

Remaining as low as possible when firing is the best way to present the smallest target to the enemy. This tactic reduces your visibility and makes it more challenging for the enemy to target you. By lowering your profile, you minimize the amount of your body that is exposed, which is crucial in combat situations where enemy fire is a concern.

This position not only helps in avoiding detection but also allows for better use of cover, thereby increasing your chances of survival. Combat training emphasizes the importance of taking advantage of the landscape and available cover, and staying low is a fundamental aspect of that strategy.

In contrast, standing tall, being in the open, or moving quickly can increase your visibility and make you an easier target for opponents, which is why those approaches are not advisable in firefighting tactics.