St. Michael the Archangel, defend    <name>    in the day of battle; be    <name>   's safeguard against the wickedness and snares of the Devil. May God rebuke him, I humbly pray, and do thou, O Prince of the Heavenly Host, by the power of God cast into hell satan and all the other evil spirits who prowl through the world seeking the ruin of souls. Amen!

Here are some good scripture passages to read and pray as well:
2 Timothy 4:18
Romans 12:2
Ephesians 5:11
James 4:7