In order to learn how to be an effective witness for Christ, look at his example. He is always witnessing: by the well of Samaria, or in the Temple of Jerusalem: by the lake of Gennesaret, or on the mountain's brow.
He is witnessing night and day; his mighty prayers are as vocal to God as his daily services. He witnesses under all circumstances; Scribes and Pharisees cannot shut his mouth; even before Pilate he witnesses a good confession.
He witnesses so clearly, and so distinctly that there is no mistake in him. He is our example to follow, to make our life a clear testimony.
His message was as clear as a running stream, not as a muddy creek, clear and transparent. His heart of love to God and man was visible to all.
You need not say, "I am true:" be true. No need to boast not of integrity, but be upright.
Then your testimony will be such that men cannot help seeing it.
Never restrain your witness, lest you offend someone; Jesus offended just about everyone before his death on the cross. (Mt. 13:21, 13:57, Mt. 26:31, Mr. 6:3, Mr. 14:27, )
Don't consult the atmosphere, or watch the clouds of storm or wind before you witness; we are to preach "In and out of season". Don't shrink at suffering persecution for Christ's sake, or the gospel, rejoice; as the wintesses before you did, that you are counted worthy to suffer for His Name.
Ac 5:40 And to him they agreed: and when they had called the apostles, and beaten them, they commanded that they should not speak in the name of Jesus, and let them go.
Study the steps of our Savior, and how he managed his trials and suffering. Then follow close in His steps. Be filled with the Spirit that He has promised to us, to empower us to fulfill all He has called us to.
He has overcome, and told us we can also. If we keep our eyes fixed on Jesus, the Author and Finisher of our faith; we will complete the call of "a witness".
1pe 2:19-24 For this is thankworthy, if a man for conscience toward God endure grief, suffering wrongfully. For what glory is it, if, when ye be buffeted for your faults, ye shall take it patiently? but if, when ye do well, and suffer for it, ye take it patiently, this is acceptable with God. For even hereunto were ye called: because Christ also suffered for us, leaving us an example, that ye should follow his steps: Who did no sin, neither was guile found in his mouth: Who, when he was reviled, reviled not again; when he suffered, he threatened not; but committed himself to him that judgeth righteously: Who his own self bare our sins in his own body on the tree, that we, being dead to sins, should live unto righteousness: by whose stripes ye were healed.