What can I do to know that I am in right standing with God?

1.  RECOGNIZE that you are separated from a relationship with God because of your sins and His holiness.  "For all have sinned, and come short of the glory of God." (Romans 3:23)

2.  REALIZE that God loves you and believe that Jesus died on the cross as payment in full for your sins.  "But God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us." (Romans 5:8)

3.  RECEIVE the risen Christ into your life by faith, and trust Him as your Lord and Savior.  Ask Him to help you walk in daily obedience to God.  "But as many as received Him, to them gave He power to become the sons of God, even to them that believe on His name."  (John 1:12)

You might pray something like this.....

Dear Jesus, I know that I am a sinner in need of a Savior.  I turn now from my sins and receive You into my life.  Thank-you for sacrificing Your life to save me, and then rising to life again that I may spend eternity in heaven with You.  Help me to live my life in a way that pleases You, for whatever time you give me here on earth.  In Jesus' name, Amen.