If you find a crack, the rim should not be used. Unbending a wheel is a skill that requires lots of practice to be a reliable repair technique. Flat Spots Flat spots can be repaired. Sometimes you can fix one by loosening the spokes at the flat spot and tightening all the other spokes in the wheel. More severe flat spots require removing two or three spokes at the damaged area, hitting the rim outward with a mallet until it bulges out just a little beyond round, then reconnecting and tightening the spokes where the flat spot used to be.
Kinks come from hitting stones, curbs or sharp edges in the road.
Keeping the tires fully inflated will reduce the likelihood of kinks occurring. Kinks are repaired easily by hitting them back into position with a hammer, or by squeezing the rim with pliers. Use cloth between the pliers and the rim to prevent tooth marks. If you have a broken spoke, simply replace it before you align the wheel. On a wheel from a derailleur-equipped bike, you will need to remove the freewheel first.