Since when a wheel bearing goes bad you can feel it more than you can hear it, and there usually isn't any deflection in the wheel itself until the bearing is pretty much shot, the way I usually check for the bad bearing is with an automotive stethoscope:
What I do is this:
- Put the car up on jack stands
- Take the wheel off of the car (if you need to loosen the wheel before jacking, do so)
- Place the stethoscope tip on knuckle (the portion the wheel bearing is inside of)
NOTE: You may need to take the caliper and rotor off of the hub to get a clear shot at the knuckle
When you are listening, you should be able to tell pretty quickly if it has the bad bearing or not. It will sound crunchy as you are turning it. A good bearing should sound relatively smooth as you turn the hub. You'll want to perform the same to both sides. You may be able to tell a difference, but there's always the chance that both sides need bearings.