To pray one decade of the rosary, first make the sign of the cross and say one "Our Father" and 10 "Hail Mary"s, then say one "Glory be to the Father" and meditate on one of the 20 Mysteries. The mysteries to meditate about include the Joyful, Sorrowful, Glorious and Luminous Mysteries.
The purpose of praying the rosary is to keep in mind certain events in our history, called the Mysteries, and thank God for these events. Pope John Paul suggested that individuals pray about the Joyful Mysteries on Monday and Saturday, the Luminous Mysteries on Thursday, the Sorrowful Mysteries on Tuesday and Friday and the Glorious Mysteries on Wednesday and Sunday. In order to pray the full rosary, start by making the sign of the cross and saying one "Apostles' Creed," followed by one "Our Father," three "Hail Mary"s and the "Glory be to the Father", and then announce the first Mystery and pray one decade. After each decade, pray "O my Jesus, forgive us our sins, save us from the fires of hell, lead all souls to Heaven, especially those who have most need of your mercy." You can pray as many decades as you would like in one session. After praying as many decades as desired, end the rosary prayer session by praying the "Hail the Holy Queen," then say "In the name of the Father, the Son, and the Holy Spirit. Amen."