Anytime at all; saints are 24/7! They are always there to assist you
It is called a litany, as in Litany of Saints.
Catholics don't pray to saints they pray with saints to god with their prayers helping us. We also pray with Mary to pray for us. hence we don't say 'St.Andrew i pray to you' we say 'St.Andrew pray for us'
Saints are believed to be divinely connected with God, like a direct line. So we pray to them to ask them to ask God to help us, or pray to God for us, we believe God can do some miracles, through the saints. For a Catholic, the Saints are very much alive and in heaven, and just as you would ask a friend to pray for you, you can ask the saints to pray for you as well. Catholics use the word "pray" in the traditional sense of the word, whereas most protestants use "pray" to be the same thing as worship. Catholics do NOT worship saints.
Only Catholic Christians pray to saints. Protestants Christians do not. We [Protestants] believe they were disciples/apostles of Jesus, but we don't ask the them to pray for us.
Let us pray.
Worship The One True G-d of the Heavens. Pray to the Father through Jesus the Christ. Personally for me this would be wrong to pray to the Saints-they are the true holy ones who gave their lives for the One True G-d.
Here on earth few of us really know how to pray. The saints in heaven do know how to pray and can pray with and for us to God for special favors. They intercede on our behalf much as a lawyer would intercede for us before a judge. A lawyer knows the ins and outs of the system to get things done. Consider the saints your lawyers in heaven.
In reality, we do not so much as pray 'to' the saints as 'through' the saints. We ask them to join us in our prayers to God for a special intention. It is no different than asking a friend to pray for you or your intentions. The saints are part of the Mystical Body of Christ, as we also are if we are in God's favor. Another term is the Communion of Saints. We are one big family divided only by our current state of existence.
We chant and pray...well...prayers and praises to the Lord our God and prayers asking angels and saints to pray for us. We give praise and thanks to Him and we mainly ask him to forgive our sins and save us from the fires of hell.
The Rosary is a means of meditating on the Life of Christ, the Saints there are no saints (on) the beads, but they may be included in the meditations on the Life of Jesus. Saints (to include the Blessed Mother) are not prayed to, rather, we ask them to pray for us.
Saints do not hold quite the same role for Lutherans as for Roman Catholics. The Lutheran liturgical calendar designates days of commemoration to believers who have gone before us as examples of Christian virtue and as people of faith. Lutherans pray in the example of the Saints and pray to be likened to them in faith. Lutherans do not, however, petition to the Saints for prayer, protection or blessing. If we are praying to God for patience and strenght, we may pray that He grant us a patience like that of the Virgin Mary. If we are praying for understanding and peace, we may pray that we are granted a sense of peace and understanding like that of Saint Francis.
Catholics believe in the Communion of Saints, as do many other Christian sects. We are all part of the Mystical Body of Christ - those living on earth in a state of grace, those in Purgatory waiting for final redemption and those in Heaven who stand before the Lord. We do not so much as pray TO the saints as THROUGH the saints or to join us in our prayers for a specific intention. We ask them to present out intentions to God for his intervention. It is no different than asking a friend to pray for us or for our intention. What's more, the saints have an intimate relation with God and know how to pray whereas we, on earth, are frequently lacking in a capacity to pray properly.