Do you have a serious problem that requires the help of God? Prayer, self-denial, and works of mercy are the path to salvation and the path to obtaining the grace and providence of God.
But if you have a particularly difficult problem, and nothing seems to help, not even prayer and fasting, then I recommend a novena to Saint Joseph using this prayer:
The Prayer of Praise to Saint Joseph
Choose the number of times you will say the prayer each day, for nine days, and ask Saint Joseph to intercede, with the Blessed Virgin Mary, before Jesus Christ to obtain your petition.