Hardened Hearts

I was reading the bible and I came across the part in the old testament where God warned Moses that He would make the Pharohs heart hard against Him. (Exodus) It has made me wonder ever since reading it.
How do you reach out to someone whose heart is so hard against Christ? Do you cower in fear and not talk about it, just in case it makes them feel uncomfortable? But wouldn't that give Satan the upper hand? How do you help those that for some reason have turned away from God? How do you explain to them that even though they are suffering God knows and He wants them where they are so that they can come to Him.
I am pretty darn sure I understand the answers to these questions but I just don't know how to relay them in terms that won't make people just shut me and Him out.
I will tell people that I am a Christian without hesitation and I long for them to experience Christ and what He has done for us. Do I wait?
How do you soften a harden heart?
So I just keep praying that God will give me the guidance that I need. I want to talk about God with them, but I find myself slightly hesitate. They may not want to hear it. I guess though that the biggest thing against God is when we keep silent. How do you know when it is right to talk? I feel that it is right all the time, but am I wrong?
Lord help me to understand. Help those whose hearts are so hard against you and have them come back to your arms and your safety. In your name I pray, Amen.