First and foremost, listen! The most common and most easily identifiable symptom of a bad wheel bearing is an audible one. If you notice a grinding or grating noise coming from your wheel or tire, take note that this is very likely caused by a bad wheel bearing—especially if the noise gets louder as the vehicle accelerates.
Another revealing sign of bad wheel bearings: A car that feels loose as you drive it. Looseness can be difficult to convey, but basically, it refers to steering your car and finding that it seems less responsive or less precise than usual. Loose steering is not always due to a problem with the wheel bearings, but it very often can be. Sometimes the wheel bearings can become worn down, which causes them to loosen within your wheel assembly.
A related phenomenon is pulling. When you drive, does the car go where you tell it to or does it seem like it has a mind of its own, veering in a particular direction? Again, this is not always because of a problem with the wheel bearing, but that can certainly be a culprit.