Prioritize keeping shivs for those intense clicker encounters since you'll definitely need them for the stealth kills, and they're essential for those locked doors with good loot inside. When you spot a clicker, watch their movement pattern - they do this specific swaying motion before entering their echo-location state which is your ideal window to approach from behind. The stealth grab timing is critical here, press triangle to initiate and then quickly follow with another triangle press right as the prompt appears, or they'll break free and alert others.

Regular infected and humans can be handled with standard stealth takedowns, so don't waste precious shiv resources there especially since normal difficulty gives you just enough crafting materials to stay equipped. For locked doors, you'll notice a distinct padlock icon when you're close enough - these usually hide weapon parts or supplements behind them, making them worth saving a shiv for. When playing as abby though, you'll need to be more selective since she relies on shivs for both clickers and those heavily armored enemies that start showing up later in her sections

Quick count of action windows: 2-3 seconds for clicker approach, about 1 second for the stealth grab input, and roughly 4 seconds for the full door opening animation where you're vulnerable to nearby enemies