I nailed a 13-mile, ~4000-feet hike on Mt. Diablo in east bay of SF Bay Area without blisters! I'm really happy because it's really for me to get blisters on feet. Usually when I discover them, they look like torn-off skins already.
Recent, I've been studying tips for backpacking. One tips from the book Joy of backpack was about using duck tape to avoid blisters. Blisters happen when your feet rub against socks as you walk, when certain areas of feet get sore and even hot, be cautious. To reduce that, simply cut a piece of duck tape and stick to your foot -- the areas that are easy to get blisters, such as the inner sides of both my toes, balls of my feet, as well as heels when going steep uphill.
For this strenuous Diablo hike, I put three pieces on each foot. Although I can still feel some soreness when I walk, I didn't have new blisters.