Here's the official stand from the Catechism of the Catholic Church:
"Being more closely united to Christ, those who dwell in heaven fix the whole Church more firmly in holiness ... [T]hey do not cease to intercede with the Father for us, as they proffer the merits which they acquired on earth through the one mediator between God and men, Christ Jesus. ... So by their fraternal concern is our weakness greatly helped. (CCC 956)
Also See CCC 2683-2684 (Saints as Companions in Prayer)
A Few Prayers:
Below are a few very short prayers to some Bible Saints. These brief prayers are sometimes called "Aspirations."
O St. Moses, a holy leader of the people of Israel, please pray for me/us.
St. Joshua, you led the people of Israel into the Promised Land with obedience to God. Please pray that God will help me to lead those I am in charge of.
Holy Mary, gentle mother of God, pray for me/us.
St. James the Greater
O St. James who left everything behind to follow Jesus, please pray for me/us.
St. John the Evangelist
O St. John who reclined upon the chest of Christ and was left to take care of His mother, Mary, please pray for me/us.
St. Salome please pray that I may effectively encourage my children to cling to the Lord.
St. Martha, please pray that I/we may overcome worries and instead embrace the message of Christ.
O St. Lydia, you opened your heart to the Good News of Christ and offered your home to the earliest Christians of Philippi for worship; please pray for me/us.
St. Timothy, a faithful disciple of St. Paul who suffered from frequent illnesses, please pray for me/us.
Sts. Aquila & Priscilla
Sts. Aquila and Priscilla, your marriage was devoted to the Lord; please pray for my marriage.
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