Sometimes I think we Believers focus on the "do" kind of witness rather than the "be" witness. The word witness is used both ways in the scriptures, but more often when it comes to us it is the "be" kind of witness. We are God's witnesses when we let Him work through us. ''
That is the whole victory. Read this verse:
"For whatever is born of God overcomes the world; and this is the victory that has overcome the world -- our faith." 1 John 5:4
Focusing on the "do" kind of witness can even get us all focused on actions rather than just believing and living in Jesus. Now, if God calls you to do witnessing, go for it. But I think we make it too hard sometimes, too complicated.
It can be as simple as saying to someone sick, "Let's ask Jesus to heal you."
Just mentioning Jesus' name is powerful.
Or, you can just tell them what Jesus has done for you lately. If you are walking with Him, than you have a story to tell, a story someone needs to hear.
Don't make it hard. Just let the Spirit move in you. How? Just get out of God's way and let Him work. Most of the time you won't see what He does. And that is just fine. We don't need to know what He is doing. If we need to know He'll tell us.
Just be there. Just be available. And just love.