The problem of people who feel fearful or guilty regarding evangelism is compounded by the barrier of inadequacy. Many who would otherwise wish to share their faith feel totally unprepared to do so. We can overcome this barrier if we remember two things. First, our adequacy comes from Jesus, not from ourselves. Apart from Him, we are utterly incapable of changing other people, let alone leading them to Christ. “Such confidence we have through Christ toward God. Not that we are adequate in ourselves to consider anything as coming from ourselves, but our adequacy is from God, who also made us adequate as servants of a new covenant” (2 Corinthians 3:4-6a). When we engage in the process of evangelism, we are committing ourselves to something that cannot occur unless God does it through us.
Second, if we are unprepared to share the gospel or to answer the objections people may have, the solution is to “Be diligent to present yourself approved to God as a workman who does not need to be ashamed, accurately handling the word of truth” (2 Timothy 2:15). Most believers do not know how to make a simple gospel presentation with an unmarked Bible, but this is not difficult to learn. Similarly, most do not know how to answer the common questions that are likely to surface when we seek to plant the seed of the Word. However, this need not prevent us from going into the field, since good answers are readily available. As Howard Hendricks put it, "If you fail to prepare, you prepare to fail."
Taken from Ken Boa’s Handbook to Spiritual Growth