The causes for getting to heaven are the same as the actions needed to obtain the Liberation and Understanding of Buddhahood.
These are Generosity, Morality, Patience, Perseverance, Concentration, and Wisdom.
At the very least, to get to Heaven, we need Generosity and Morality. The greater our practice of these are, the greater our experience of heavenly pleasures. By adding each new perfection, our experience of Heavenly pleasures moves to another level.
From the point of view of Buddhahood, by recognizing that each level of perfection is not an end in itself, recognizing that complete Liberation from the cycle of suffering requires Buddhahood, we use the energy and enthusiasm we receive from these levels of perfection to help us reach further and further until we know that we have ended all possibility of unwilling rebirth in suffering states of existence.
In the Buddhist path, each perfection leads to the next. Generosity leads to not harming others, which is the basis of Morality. Maintaining Morality in difficult situations requires Patience. Maintaining Patience requires Perseverance. Through our efforts to develop Perseverance, we develop Concentration. Through the power, clarity, and strength of mind that comes with Concentration, we develop Wisdom.
So, whether our goal is Heavenly Rebirth or Buddhahood, the path is the same – Practicing and perfecting Generosity, Morality, Patience, Perseverance, and Wisdom.