People cannot become followers of Jesus if they have not heard about Him, and what He has done to save us (Romans 10:14).  Although there are millions of Christians in the world today, many of their friends and colleagues have not yet heard them speaking about Jesus Christ.  Some believers think that their faith is a private matter only for them; but Jesus told us to make more disciples for Him (Matthew 28:19).  Many others are simply afraid of an adverse reaction from friends and colleagues.  But Peter says, "Don't be frightened!"
 
Some believers have the gift to preach or teach publicly, but everybody who honours Jesus as their Lord and Master should want to speak well of Him.  Most of the opportunities will come when we are questioned about our faith or lifestyle. So each born-again Christian should be ready with simple answers such as, "I believe in Jesus so I am learning to obey and follow Him"; or, "I know that I am going to heaven because Jesus died for me".  Of course, these answers will probably trigger more questions, but trust the Holy Spirit to help you (Acts 1:8) - and never be ashamed to say when you do not know, because you are willing to find out and tell them later.

The key to confidence in speaking about Jesus is how dearly we hold Him in our hearts.  If He is just a religious teacher who we admire, fear will stop us exalting Him.  But if He fills our hearts - higher than every other thought and desire - then nothing can stop us from announcing Him to the world (2 Corinthians 5:11-15).  
 
Part of the reason for going to church and Bible study is to get prepared to answer questions about Jesus.  This is a significant part of any church leader's responsibility (Ephesians 4:11-13).  We should not just listen to teaching but use it to prepare ourselves to answer questions.  Many people want to find the secret of life and hope after death: they will search throughout the internet, but the answer is only found in Jesus (Acts 4:12).  But your friends may never know how to be saved if you are not prepared to tell them.  If you belong to a workplace Christian group, why not use that time to prepare your hearts and your answers - it could save someone's life.