How can you tell if your brake booster has a vacuum leak?

You can identify a vacuum leak in your brake booster by listening for a hissing sound around the booster area while the engine is running. A hard brake pedal that requires more effort to press can also indicate a leak, as the booster isn't providing the necessary assistance. Additionally, checking for a drop in engine RPMs when the brake pedal is pressed can signal a vacuum leak. If you suspect a leak, visually inspect the vacuum lines and connections for any signs of damage or disconnection.