I have flat feet and my feet hurt alot. The pain is caused by a condition called plantar fascitis. because the foot is flat it causes the muscles and fascia on the bottom of the foot to become tight and pull. several things will help:
1. stretch your calf muscles. stand on a step backwards, hold on to the railing with one hand, position both feet so that your toes are on the steps and your heels are hanging off the steps then lean back slightly, you will feel a pull at the back of your calf because of the tightness you probably have. Do this exercise daily and when ever you think of it. It will help.
2. get a good pair of sneakers, new balance is recommended by the podiatrist here. They say the runners are best and the higher the shoe number the better example New Balance 321.
3. Try Dr. Scholls sports gel orthotics for women, they can be purchased at the drug store.
4. If the pain persist see the podiatrist and have custom orthotics made.
5. My podiatrist does a taping technique inwhich she tapes the bottom of my foot, she puts the tape on like a moccassin and I wear it a few days and it helps relieve the swelling and pain.
6. Put a water bottle in the freezer then use the frozen water bottle to roll your foot back and forth to help relieve some of the pain.
There is surgery but it should be your very very last option. The surgery is quite riskly and can cause lasting disability. Google Plantar Fascitis for more information