For wheels with rim brakes, you can easily check the wheels mounted in your bike by rotating the wheel and looking next to your brake pads to see if the wheel is true. If you notice a discrepancy in the wheel then it should be repaired.
Wheels with disc brakes are slightly more difficult to check. The best way to do this is to look along the fork (front or rear) to identify any irregularities. If this is the case, have a bike shop check and repair the alignment as soon as possible.
Bear in mind that irregularities in a wheel can also be caused by the tyre not being mounted correctly. There may also be a construction fault in the tyre. Therefore, always look at the movement of the rim and not the complete wheel.