There seems to be some debate over the meaning of the term, "Evangelical Christian." I identify myself as an Evangelical and identify others who have common beliefs as Evangelicals. Personally, I believe that an Evangelical Christian is one who believes the following:
With respect to Jesus Christ:
Evangelicals believe that Jesus Christ is the Son of God and Messiah (John 3:16, Matthew 11:2-6, Issiah 53), that He was born of a virgin (Issiah 7:14, Matthew 1:18-25), that He lived a sinless life (2 Corinthians 5:21), that He was crucified for the sins of humanity (1 Corinthians 15:3), and that He raised from the dead on the third day (1 Corinthians 15:4). Evangelicals believe in the trinity (Father, Son, Holy Spirit) and believe that all authority in heaven and on earth has been given to Jesus Christ (Matthew 28:18).
With respect to Salvation:
Evangelicals believe that salvation is received by God's grace through faith and that it cannot be earned (Ephesians 2:8-9), that all have sinned and fall short of God's glory (Romans 3:23), and that salvation comes through the shed blood of Jesus Christ (Acts 4:12, Hebrews 9:22). Evangelicals also believe that a personal relationship (born again) with Jesus Christ (confessing sin, seeking repentance, forgiving others, and sharing the Gospel) is vital to having proper fellowship with God (John 3:1-21, 1 John 1:9, Matthew 6:14-15, Matthew 7:21-23, Luke 15:7).
With respect to the Bible:
An Evangelical Christian believes that the Bible is the inerrant Word of God, that every letter of it was the inspired work of God, and that the Bible is to be used for teaching, rebuking, and correcting (2 Timothy 3:16-17). Evangelicals believe that Christ has fulfilled the Law and that there is a new covenant between God and humanity (Matthew 5:17-18, Jeremiah 31:31-34).
With respect to God and Satan:
Evangelicals also believe that Satan exists, that he is evil, and that God will judge Satan and his demons (Revelation 20:10). Finally, Evangelicals believe that God cannot lie, that He does not change His mind, that He is all powerful, all knowing, all loving, and all forgiving (Numbers 23:19, Job 40-42:6, Psalm 103).
It should be mentioned that Evangelicalism is not a sect or denomination. Lutherans, Methodists, Baptists, Presbyterians, and even Roman Catholics (etc.) can be Evangelicals. The fact that one is from a certain denomination does not disqualify oneself from being an Evangelical. However, at the same time this does not mean that everyone who adheres to a certain denomination is an Evangelical. Evangelicalism is about a personal relationship with Jesus Christ, not about attending church, keeping church traditions, and other external rituals (besides baptism and the Lord's Supper which are commanded). While it may be of benefit to do these things, they are not one's salvation.
The sinner's prayer is a prayer that one prays when he or she desires to become a Christian. One who prays the prayer must believe that he or she is a sinner, that Christ died for his or her sins, and that He is willing to forgive all of his or her sins.
The Sinner's Prayer:
"Dear Jesus, I believe that I am a sinner. I believe that I need to be forgiven for my sins. I believe that you died on the cross for my salvation and that you conquered death by rising from the grave on the third day. I ask you to forgive me for every sin that I have committed. I ask you to come into my heart and begin a personal relationship with me. I ask you to give me the strength to repent from my sins and the strength to forgive others. I ask these things in Jesus' name, Amen."
After you have prayed the sinner's prayer be sure to find and attend a Bible believing Church. If you have a Bible start studying the book of John. Find some Christian friends who are sincere believers and knowledgeable in the Word of God. When you have temptations, ask God for strength, when you have anxiety, pray for God to comfort you. Be aware of those who will try to deceive you and pray for your enemies and those who persecute you. To God be the glory, amen.