How to prevent bad posture in the future. and what to do if you have flat feet.

Awareness, Genetics: Things like bad posture and flat feet most often have to do with the skeletal structure one was born with. Posture can be improved upon with exercises such as pilates and yoga, and increased awareness of one's carriage. Flat feet are, sadly, permanent. One cannot create arches where they do not exist. However if the flat feet are symptomatic, orthotics or other devices can be most helpful.

Need foot orthotics: You may want to be fitted for custom foot orthotics.

Orthotics : Would be a good start for the flatfeet, they may also help the posture. A conscious effort to improve your posture will likely help and strengthening excercises may be of value....

Replacement insoles: These can be custom made orthotics, made specifically for your individual feet, by seeing a podiatrist. For otc supports, i really like spenco medical products. Try the polysorb cross-trainer, walker-runner or total support styles to get more support in your shoes.