Run silent: despite limitations to speed, repairs and reloading, silent running decreases noise made by your submarine.
Keep out of enemy sonar detection ranges: classifying the enemy and understanding their sonar detection capabilities allows you to stay outside of their detection threshold. Be careful though, a sudden drop in speed by the enemy, or a sudden turn to clear their baffles can quickly and significantly increase their passive sonar detection range.
Stay slow and don’t cavitate: speed equals noise. Be sure to maintain a safe distance from the enemy if you intend to move at faster speeds.
Put the layer between you and the enemy: if a layer is present, keeping it between you and your contact will decrease the sound transmission between you both (unless too close). This can be useful for sneaking in closer or for firing weapons, as the layer will decrease some of the noise from your transient.
Stay off the surface: enemy radar has a long range. You should not ever surface, except in the case of an emergency to save your submarine from flooding. But if enemy warships or aircraft are in the area, expect a rapid attack. When using masts, don’t leave them exposed. Get the data you need from them and get them down again quickly.
Get on their six: positioning yourself at an enemy’s 6 o’clock (directly behind) will put you in their baffles if they do not possess a towed array or are moving too fast for their towed array to be effective. When firing weapons, being in their baffles should decrease or even prevent them detecting noise from your transient.
Use decoys: firing a decoy and keeping it between you and the enemy may cause weapons and the enemy to focus on its position rather than yours.