The key to motivating anyone to undertake any activity is to effectively link the resources required (time, effort, skills, knowledge, money) to the goal (their own goal or yours) using the other person's personal values.
In order to use this effectively, you will need to know and understand the other person's values - what is important for them. Use the lowest level value necessary (reserve higher level values for the most important goals).
Everybody does something because they find personal value in doing it. For example, purchasing food is commonplace, 99.9% of the world use something of value (money) to buy something of greater value (food). Food has a higher value than money because it sustains life. When you are hungry, the value of food increases - you are prepared to spend more in exchange.
Most poor leaders in business expect people to be motivated simply because they are paid a wage - these leaders need to remember that money itself is a means of exchange and rarely motivational when it is already earned - and few people ever have 'too much' money.
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