The key to having God listen is threefold: having faith, persistence, and the acceptance of suffering.
If one is praying without determination and faith, one insults God.
If one prays in suffering, joined to the Cross, one is not praying to God but with God. That is the key to answered prayer-praying in the Divine Will.
Most of the time people pray too quickly, and without what I would call intercessory pain. Christ invites us to join Him in suffering, a topic I have covered on this blog many times in the perfection series and in posts on suffering.
When God allows us to suffer, He is inviting us to enter into the mystery both of our own purification and the reparation of sins and failings. See the reparation series a few weeks ago.
However, prayers are tainted by our egos which means that pure prayer can only come from complete objectivity and renunciation of our own wills.
When we pray in Divine Providence, prayers are answered. But, this means dying to self.
Giving up our own ideas on how prayers should be answered is a beginning, a moving towards humility.
Pray with humility and openness, in suffering.
God is Good.