Assurance of Salvation
(1) Make Jesus our master and don't keep that a secret. (includes repenting from sin)
(2) Believe Jesus died for our sins and that God accepted his sacrifice by raising Jesus from the dead.
We will be saved from hell and spend eternity with God.
Immediate Context (always read the immediate context of the verse you are memorizing)
If you openly declare that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. 10 For it is by believing in your heart that you are made right with God, and it is by openly declaring your faith that you are saved. 11 As the Scriptures tell us, “Anyone who trusts in him will never be disgraced.” 12 Jew and Gentile are the same in this respect. They have the same Lord, who gives generously to all who call on him. 13 For “Everyone who calls on the name of the Lord will be saved.
Excerpts from Commentaries
If you openly declare that Jesus is Lord
"Not a simple acknowledgment that He is God and the Lord of the universe, since even demons acknowledge that to be true (James 2:19). This is the deep personal conviction, without reservation, that Jesus is that person's own master or sovereign. This phrase includes repenting from sin, trusting in Jesus for salvation, and submitting to Him as Lord. This is the volitional element of faith." The MacArthur Bible Commentary
"we are acknowledging his rank or supreme place. We are pledging our obedience and worship; we are placing our life under his protection for safekeeping. We are pledging ourselves and our resources to his control for direction and service. ... The gospel message in a nutshell is confess and believe and you will be saved. There is no reference to works or rituals" Life Application New Testament Commentary
"In view of the fact that "Lord" (Greek Kyrios) is used over 6,000 times in the Septuagint (the Greek translation of the OT) to translate the name of Israel's God (Yahweh). it is clear that Paul, when using this word of Jesus, is ascribing deity to him." The NIV Study Bible
"does not mean that a spoken affirmation of one's faith is a 'work' that merits justification, but such confession does give outward evidence of inward faith, and often confirms that faith to the speaker himself" ESV Study Bible
What does it mean to make Jesus your Lord?
and believe in your heart
"Saving faith consists of three elements:
"In Biblical terms the heart is not merely the seat of the emotions and affections, but also of the intellect and will." The NIV Study Bible
that God raised him from the dead
"Christ's resurrection was the supreme validation of His ministry (John 2:18-21). Belief in it is necessary for salvation because it proved that Christ is who He claimed to be and that the Father had accepted His sacrifice in the place of sinners (4:24; df. Acts 13:32,33; 1 Peter 1:3-4). Without the Resurrection, there is no salvation." The MacArthur Bible Commentary
"Paul does not mean that people need to believe only this individual event with no understanding of Christ’s death, but rather they need to believe in the resurrection along with the whole complex of truth connected with it, particularly Jesus’ sin- bearing death in mankind’s place, followed by his resurrection that showed God the Father’s approval of Christ’s work (see note on 4:25 )." ESV Study Bible
you will be saved
"This key word basically means "deliverance" or "rescue". The power of the gospel delivers from:
Great online Gospel presentation 'tract'
Other verses on assurance of salvation
Note the different conditions for the assurance.