Performing extra voluntary acts of worship, after the obligatory ones, is one of the greatest ways that a person can increase the chances of their du’a being answered. The evidence for this is the hadith qudsi:
On the authority of Abu Huraira who said: The Messenger of Allah (upon whom be Allah’s blessings and peace) said: “Allah the Almighty has said, ‘Whoever has mutual animosity with a friend (wali) of Mine, I declare war upon him. My servant does not draw near to Me with anything more beloved to Me than the religious duties that I have imposed upon him; and My servant continues to draw near to Me with supererogatory work such that I love him. And when I love him, I am his hearing with which he hears, his seeing with which he sees, his hand with which he strikes, and his leg with which he walks. Were he to ask of Me, I would surely give him; and were he to ask Me for refuge, I would surely grant him it.” (Recorded in al-Bukhari)
You can find a detailed explanation of the meaning this hadith here. What it shows us in brief, is that if we increase our voluntary acts of worship, such as prayer, fasting and giving charity, Allah will love us, and when Allah loves us, all of our du’as will be answered.