Samadhi is the final limb of the eight-limbed path of Yoga (Ashtanga). The other seven limbs include ethical guidelines, prana control, asana mastery, concentration, etc. Although most yoga literature lists the eight limbs of yoga in the same order, the yogin does not have to follow that order. You do not have to master one limb and then move to the next one. Everyone has a unique way of tackling them. But the last one, Samadhi, definitely requires mastery of the other seven limbs.