Will power, in a sense, is the ability to overcome the immediate want or temptation of something now to increase some sort of value in the future. Practicing will power could be not buying something you want, getting up early, exercising, saving money, or even saying yes to help out a friend who needs help moving when you don't want to. You are avoiding the want of something now for something else in the future.
For the most part, people are lazy. We do things the fastest and easiest way. If we become hungry we order a pizza. If we get bored we take a nap or eat. When the car gets dirty, we pay someone to wash it. We pay others to do the actual work. Sometimes laziness actually causes us to lie. For example, if a friend needs help moving a couch so we convince ourselves that we are busy or aren't feeling well. All of these things are easier and are not exercising our will power.
I try to practice will power everyday. I try to do something everyday that I don't want to do to. Sometimes that is avoiding beer, going for a walk when it is cold outside, skipping lunch with coworkers to save a few bucks, working out when I am tired, or skipping dessert. No matter what it is, I seem to feel stronger afterwards.
On the flip side of saying no, it seems when you say yes to helping someone you feel stronger else. Saying yes to help others is very fulfilling. Helping others is sometimes hard, but the returns almost always outweigh the effort. I don't think I know anyone that likes to move couches or beds for fun, but you always feel better afterwards. Or how about cooking a meal for your friends and family? It can be a lot of work, but it is always a great time and way less expensive than going out.