You either just started exercising or have been for a long time. One of the most important things to have are a good pair of running shoes. Where to begin? I recommend going to a specialty running store to be properly evaluated and fitted. They are knowledgable and although charge are retail prices, you are getting excellent value. They typically will bring out several shoes with varying brands and have you try them on and can even run with them outside. Also, depending on the store, you can run with them for several weeks and if they do not feel right, they usually will take them back for a store credit and try to get you in to a different shoe.
The biggest takeaway, in terms of shoes, is that the shoe feels comfortable to you. Studies show that if you perceive the shoe to feel good, then you will likely enhance your performance. Shoes generally last for 300-500 miles for serious runners, but for typical gym/workout people 6-8 months is a good rule to follow.