How? By knowing His purposes for your life, which is to conform you to the image of His Son.  His Son, who was obedient to the will of His Father and lived a perfect sinless life of service to others.  This life would be sacrificed as the perfect atonement for the sins of humanity.  Everyone is offered the gift of salvation by believing on Jesus and following after Him as a disciple.  Here is where the journey begins and here is where many have faltered.  Those who are called by God and accept the gift are not immediately taken out of this world but are called to a life that may be difficult as it stands counter culture to a world opposed to God.  The good news is that God will go with us, guiding and strengthening us as long as we purpose in our hearts to follow after Him.