I would HIGHLY recommend getting a pair of insoles. Here is a random site, and not necessarily the brands or types I would recommend, but just so you get an idea of what I am talking about
The last pair of shoes I bought were a pair of Nikes and were fairly comfortable on their own, but they were sold to me by a very persistent salesman who was, lets just say, EXTREMELY enthusiastic about his job and about selling some insoles. He got in my face and measured my feet, and informed me that I have very flat feet (a fact I am already well aware of). He made it very clear that he thought I needed a pair of insoles, and finally he convinced me to buy a pair. I figured why not, they are only $20.
Turns out to be one of the best purchases I have made in a LONG time. He helped me find a pair that were fitted to my foot size, and all you have to do once you open the package is simply slip them in your existing shoes. You can also transfer them between any pair of shoes, anytime you want. So whether you are at work, at school, or out hiking/playing sports, your feet will be as comfortable as possible.
I sound a bit like a salesman myself!
Get a pair! You won't regret it. They sell them at every local store that sells shoes.