A: Adoration - Give God praise and honor for who He is, what He's done, and what He continues to do in our lives. (I've also seen this letter listed as "Acknowledge")
C: Confession - We will continue to fall short of His holiness and should confess our sins to Him with a sincere heart of repentance.
T: Thanksgiving - Telling God what we're grateful for and giving Him thanks for his goodness, kindness, mercy, grace, etc.
S: Supplication - Bringing our requests to God for the needs of others and ourselves.