Below in simple outline form is one method of sharing the gospel that I have found to be simple and easy to understand.
1. God's demand: Perfection
See also: Psalm 5:4; Habakkuk 1:13
2. Man's condition: We are sinful, not perfect
See also: Romans 3:10, 3:22–23; James 2:10; Ecclesiastes 7:20
3. God's provision: The Lord Jesus Christ
See also: Romans 6:23; 1 Peter 3:18
4. Man's response: Believe in Christ
See also: John 3:18, 3:36, 20:31; Acts 13:38–39
Note: to "believe" in or on Christ means to trust Him as you might "believe in" your best friend or your spouse. It is not merely believing certain truths about Him; it means you are depending upon Him to do what He has promised to do, to give eternal life to those who do believe in Him.
5. God's guarantee: Eternal life
See also: John 5:24, 6:47, 10:28–29
If you commit these five major points to memory, along with a few corresponding verses with each point, you will always be able to explain the way of salvation to others.
Keeping the main thing the main thing
Virtually every time you witness, the real issue will be: Are we saved by grace or by works? Some think that although works cannot save by themselves, they certainly can't hurt! When it comes to salvation, however, works cannot save. By inserting good works into the salvation formula, the true biblical gospel is corrupted so that it becomes a false gospel that does not save. Consider just three key passages:
Never forget: Salvation is by grace alone, through faith alone, in Christ alone. It is never by works, nor can one achieve it by a combination of grace and works. This is the heart of the true gospel. You will not be effective in winning others if you pollute the gospel of grace by the addition of man's good deeds. Good works are expected by God from those who are His children after they are in His family by faith in Christ.
God always calls for good works after one has salvation, never as a means of achieving it.
Give the message clearly
By clearly I mean using Bible words and phrases with Bible definitions — refusing to add to God's Word things that simply are not there.
See also: Isaiah 8:19–20; 2 Corinthians 3:12
By simple I mean that as you express the clear gospel of God's grace you do it in words that anyone can understand. You may be biblically clear in your doctrine, yet not be simple; and you may be simple (easily understood), yet fail to be Scripturally clear.
See also: 1 Corinthians 2:1–5; 2 Corinthians 11:3
Be loving, yet give the gospel with boldness
See also: 2 Corinthians 5:14; Acts 1:8, 4:13, 4:29; Colossians 4:5–6
Be faithful (consistent) in sharing Christ
See also: Ecclesiastes 11:1, 11:4, 11:6; Luke 16:10; 1 Thessalonians 2:4
Know the gospel thoroughly
See also: 1 Corinthians 15:1–4; 2 Timothy 2:15, 2:23–26
Make sure your life enhances the gospel
See also: Romans 12:1–2; Ephesians 2:10; 1 Corinthians 6:19–20; 1 Thessalonians 2:1–13, 4:1–8
Use the Bible when you witness
See also: Luke 24:27, 24:32, 24:44–45; Matthew 24:35; Acts 17:2–4; 2 Timothy 3:16–17; Hebrews 4:12
Depend upon the Holy Spirit
See also: John 15:26–27, 16:7–11, 16:13–14; Acts 4:8, 4:31, 13:9; Galatians 5:16, 22–26; Ephesians 4:30, 5:18
Be prayerful — before, during, and after you witness
See also: Romans 10:1; 1 Timothy 2:1–4; 1 John 5:14–15
Memorize Scripture relating to salvation, assurance, and beginning the Christian life
See also: Psalm 1:1–3, 119:89, 119:105; Hebrews 4:12