There are two kinds of motivation extrinsic and intrinsic motivation. The first one is used with incentives and the second one is a real self motivation. Intrinsic motivation is more effective in the long term because it means that the person has a real interest in doing something he likes.
Usually we see that most people try to motivate others with rewards and incentives to achieve a goal, however most of the times is creates short term results because the person has no real interest in doing that.
For example, a student that has to pass a test, will be motivated by the grade, however he has no real interest in learning the topic so once he has achieved his goal he wont have anymore interest in learning more about the topic.
On the other hand, a student that wants to study a topic because he likes it and he thinks that is something valuable for his life, will be much more motivated and achieve better grades. This is called intrinsic motivation.
To create intrinsic motivation in a person you have to make him engage in the topic or action, you need to let him know why it will benefit him and how is going to improve his life however. Intrinsic motivation has to come from the inside out of the person, is difficult to create in someone else because he needs to have that real interest – you can’t force him.
If a teacher wants to create real interest in students he needs to engage them in the topic by creating an environment of interactivity and live case studies, the students need to perceive the topic as interesting and useful in their lives.