Summarize this article:

If you start feeling skin irritation while running, stop and check your shoes for debris right away. Even the tiniest pebble can rub against your skin, causing a painful blister. It's always a good idea to check your shoes for debris before you go running. You will typically experience hot spots, which are characterized by pain and redness, before a blister forms. If you can, it's best to take action to prevent further skin irritation at this point. If you need to continue running, you can apply a protective covering to the affected area, such as moleskin, a water-based gel-pad dressing, a liquid bandage, or even duct tape. These will all help prevent further friction from damaging your skin and creating a blister. You can also try applying petroleum jelly, but this will only provide temporary relief, as the heat and moisture in your shoe will eventually cause it to dissolve. Moist feet are susceptible to blisters, so if you're starting to feel some friction and your feet are wet, do whatever you can to dry them out before you continue running. Carrying an extra pair of socks with you while you run is a great idea, as you can quickly slip off the damp socks, put on the dry ones, and keep running. You can also try applying a foot powder that is designed to keep your feet dry.

Summary:
Remove foreign objects from your shoes. Treat hot spots right away. Get your feet dry fast.