This depends very much on the individual you are trying to motivate and the task at hand. Money may be something that motivates one person a lot, whereas someone else is not at all driven by a monetary reward, for example. However, a very long and arduous task is unlikely to be undertaken if the monetary reward for it does not match its nature. Many people will reward themselves in some way once they achieve their goal. Some leaders and managers, therefore, simply ask the person they want to motivate what will work in their case. Usually, a mixture of extrinsic and intrinsic motivation leads to the best outcomes.