The best approach to motivate students is by

The best approach to motivate students is to provide them proper guidance so they find direction and purpose in learning.

Guidance builds inner, lasting motivation by helping learners set goals and see a path to reach them.

Giving suitable prizes relies on extrinsic reward, which can fade and shift focus from learning to the prize.

Giving examples all the time may illustrate content but does not by itself drive the will to learn.

Delivering a speech in class is one way teaching, unlikely to engage each learner's own motivation.

This favours intrinsic over extrinsic motivation, the enduring drive that arises from within the learner.