When presenting the gospel, there are 3 points we must cover in order for our message to be considered a biblical gospel message.
Who is Man? ~ Who is Christ? ~ What Christ did?
There is another crucial part of the message, and that is the response. If we present a false response, then we leave the person in a dangerous place.
Though someone may repent and place faith in Christ without you even telling them what to do, if we tell them that all they need to do is make a ‘decision’ (to follow Christ) to be saved then we could find ourselves damming their soul to Hell. Because if someone places the assurance of their salvation in their decision, rather than the work of God in the heart, then their faith will be in their decision, rather than in Christ. God is the one who saves. He is the one that regenerates us, making us a new creation in Christ. Until God has done this work in someone they are not saved.
God has promised to save all them that come with a broken and contrite heart, in repentance and faith. But God will do the regenerating, not man. If someone relies on a decision they made 10 years ago rather than their continued faith in Jesus (displayed in a righteous and sanctified life) for proof of their conversion then their trust is on shaky ground. Decisional regeneration (the teaching that YOUR decision saves you rather than God) has sent multitudes to Hell. We must not leave someone with the impression that their decision to follow Jesus will save them, but rather coming before God in repentance and faith, until God has done a work of conversion in their heart, evidenced in: a hatred for sin, a new love for God, assurance of salvation (given by the Holy Spirit), love for the brethren and the Word of God, to name just a few.
God will save the person in His timing, when He has brought them to a place of genuine Godly sorrow which works repentance. God may save a person before they even open their mouth, because God looks at the heart, and conversely He may keep others crying out for days, in order to bring them to a place of true repentance, striping them of all self reliance and self righteousness.