“Skilful means” (upaya) is a Mahayana ideal. It means that there is not only one kind of teaching.
Instead, the bodhisattva uses whatever method works best to help a person and bring him closer to nirvana or enlightenment.
Skillful means always knowing exactly how to respond to each situation in a way that is consistent with the Buddhist Dharma.
It means being able to perceive in someone exactly what he needs most to become enlightened.