How do you know if a spoke is loose? You can grab each pair of spokes where they cross and give them a squeeze. But the time-tested method is to put the bike on a stand, spin the wheels, and let a wrench lightly tap each spoke as it goes around. A properly-tensioned spoke makes a satisfying “ting” sound; a loose spoke will make a dull “thud.” It’s a lot like tuning a guitar, and if you’re tone deaf it pays to strong-arm a musician friend who has a good ear and get them to give it a listen for you. A proper spoke wrench is a must. Just tighten the nipple down on the spoke in ¼-turn increments until it sings in tune with its friends. You’re trying to screw the nipple down farther on the spoke, so in this picture you’d be turning it counter-clockwise. While you’re at it, you can give the wheel a quick check to see if it’s in true. Be sure to test both sides of each wheel.