The ancient patriarchs of the Pure Land School taught us to abide by the precepts and chant a Buddha's name. If we just chant a Buddha's name without abiding by the precepts and practicing virtues, we cannot be born into the Western Pure Land. As the ancient patriarchs said, "If we chant a Buddha's name with a scattered mind, even to the point of loosing our voice, it all would have been in vain". Thus, it is most important that we harbor kind hearts, say kind words and do kind deeds.
(Adapted from http://www.amtb.org.tw/e-bud/chinese/treat1.htm)