Compare this picture to the last one, and you should instantly recognize a major difference. These shoes are worn down, and need to be replaced. The wear pattern on the forefoot is immediately obvious. You can also tell from this picture that the runner has a mid to forefoot foot strike while running. The heel shoes virtually no wear.
It is also helpful to examine more than one pair of your old running shoes, if you are trying to determine your individual needs in a running shoe. Someone with a heel strike has different shoe needs than someone with a mid-sole strike. Also, you may pronate or supinate when you run. If you aren't sure bring a pair of your worn down running shoes to your local shoe store and have them examine your wear pattern. They can perform a stride analysis, and recommend an appropriate shoe. You may want to stick some air fresheners in your shoe before handing them over. As a courtesy. ;)