It is possible to fix a severe bend in a wheel by stomping on it, and to fix more subtle misalignments by truing the wheel. Truing a wheel involves altering the tension of the spokes using a spoke key.
To use the stomp technique, it is good to find a way to do it without pushing on the hub. A hole in pavement or the top of an oil drum on which to place the wheel are good options. The next step is to stomp on the wheel to make it flat. Because the wheel rim has memory, it is a good idea to push it a little beyond flat. Finally, spin the wheel to see where any curves may still remain, and repeat the process.
To true a wheel, it is necessary to have a way to tell where the wheel is wobbling, and in which direction. A truing stand is the best option, but It is possible to use rim brakes as a guide.
Place the wheel on the stand and spin it. It is then possible to see the area between the rim and the pointer to assess where the rim wobbles. Starting with the biggest wobble, check if one of the spokes near the wobble is a lot looser than other spokes. If it is, adjust it similar to the other spokes. To tighten spoke nipples, turn them clockwise.
Working with four spokes at a time, alter the tension on the spokes in the area of the wobble. To move the rim left, tighten the spokes on the left one-quarter turn and loosen the ones on the right by the same amount. Continue working on in this manner around the wheel until the wobbles are gone.