Good posture starts from the bottom up. Getting the right support for your feet is a crucial first step to maintain good posture. This means that the balls, heels, and toes of the feet need to be properly supported and balanced. They should be comfortable while standing, walking, or running. For those whose feet simply get sore from standing or walking all day, simple cushioned inserts might be the easiest change you can make. If your feet get sore in one spot during the day, it can throw off your balance and lead to improper posture. Inserts should support all aspects of the feet and have enough room in the shoe for the foot to fit comfortably.
You might consider if you are wearing the right shoe in the first place. Just like construction workers wear thick work boots, and ballerinas wear ballet slippers, there's a specific type of shoe for any activity. If your feet don’t adhere to the normal standard of support that others get from cushion inserts, you might need to look into orthotics. Finding the type of shoe that fits your specific needs may be a long process, but it will be worth the wait and the investment. Talk to a physician if you think that you need professional help finding the right shoe for your feet.