Have you heard the backpacking axiom, "Eat before you're hungry; drink before you're thirsty"? These statements are true because once you're hungry or thirsty, it can be hard to regain optimum energy. Now take that little nugget of wisdom and multiply it by a gazillion and you have the cardinal rule of backpacking foot care: Stop foot pain before it starts.
While in football or tennis it might be admirable to play through the pain, in backpacking it's just stupid. As you hike, be aware of how your feet feel, and especially if you feel any "hot spots," stop immediately and take care of them before they form blisters. In the long run, a couple of stops in a hike's first few miles will annoy your hiking partners much less than listening to you whine as you hobble and slow everyone down for the remainder of the hike.
First, be aware of any places your boot typically rubs your foot. Before you start hiking, apply moleskin, duct tape or medical tape to those areas. After you start hiking, if you feel any other hot spots, stop, take off your socks and boots, dry the affected area and apply the same to those areas as well. As you hike, monitor these areas, and especially if you feel the moleskin or duct tape fall off, stop and reapply as needed.