Allaah the Most High says:
"Indeed in this there is a remembrance for those who have a living heart, listen attentively and are awake to taking heed." [Qaaf: 37]
Therefore, if you desire to benefit from the Qur'aan, gather your heart when reciting it, focus your attention to it and focus as if you are the one being directly addressed by it. For indeed it is an address from Allaah via the path of the Messenger (sallallaahu `alayhi wa sallam).
This is because gaining complete benefit from the Qur'aan is dependent upon the object providing the benefit, the place by which it is to be received, the conditions related to attaining the benefit and the non existence of anything that may hinder the benefit from occurring. Hence the verse contains an explanation of all of these points, with the shortest and clearest of words, and those that best prove the point.
Thus the saying of Allaah: {Indeed in this there is a remembrance} has an inference to what has preceded the verse from the beginning of Soorah Qaaf up to this verse and this is what is causing the benefit.
Whilst the saying of Allaah {who have a living heart} then this refers to the place that receives the benefit and this is the heart that has life and comprehends what Allaah has sent, as Allaah the Most High says:
"Indeed this is only a clear reminder and a Qur'aan so as to warn those who have a living heart." [Yaaseen: 69-70]
And His saying {listen attentively} i.e. who turns his attention to it and listens mindfully to what is being said. This is the condition that is placed so that one can be benefited by it. And His saying {are awake to taking heed.} i.e. that the heart is attentive to it.
Ibn Qutaibah said:
"Listen to the book of Allaah whilst your heart and mind is attentive, not neglectful nor distant."
This is an inference to the matter that prevents one from attaining benefit. That is when the heart is distant and unmindful such that it does not understand what is being said, nor comprehend it.
Therefore if the cause of the benefit - the Qur'aan, is found and the place of receiving it - and that is the heart has life - and the condition is fulfilled - and that is listening attentively - and the barriers that would prevent benefit from being attained are avoided - and that is the heart being pre-occupied with something else and it being unmindful of what is said - then one attains the benefit, of being benefited by the Qur'aan. [Refer to al-Fawaa'id by Ibn-ul-Qayyim]