#1 - Cheap socks. White sport socks are white sport socks, right?? Apparently not. There are specific socks that pull away water from your foot, thereby reducing the amount of irritation to your skin from the rubbing against the sock.
Here's the best way I can explain it to those with smaller legs: Remember when you wore a pair of shorts to a water park when you were younger than went on the Flume ride? You got soaked and had a blast but for the remainder of the day, your wet shorts would ride up as you walked and would start rubbing against your inner thigh because they were wet, causing some issues to your skin. The best way to explain it to those with thighs like mine: It's that inner thigh skin feeling you get anytime you put on a pair of shorts above your knee and sweat at all. If your foot gets wet, your skin will rub against your socks causing irritation and eventually blisters.
#2 - Wrong size shoes. My normal shoe size is a 9. However, not only are sneakers often made slightly smaller than a normal shoe, but your feet swell as you run. My size 9 ASICS were great running shoes and were good for how I run (I roll my foot in. That's what the guy at the store told me. Again, extremely technical for running). Unfortunately, they were getting too tight on my feet and were probably the main cause of the blister.
So I got new shoes which are now the picture at the bottom of my page!! Those who know me well know that I love me a new pair of shoes.
My suggestion for people who are thinking of starting to run: Go to a running store with employees who love to run and aren't just looking to get a sale. Have them look at your feet. And then invest in the right pair of shoes before you begin. They will cost more money than the Champions at Payless, which I have owned in the past, but they will get you through your runs on a much better foot. If you get cheap shoes, you will end up having to buy another pair sooner anyway and the expense will even out, but your poor feet will not be happy with you.
Off to my two mile run that I skipped yesterday!