First, you must focus inward and examine your personal relationship with Christ. Is He at the center of your life? When things go wrong do you look to Him instead of trying to fix things yourself? When things go well, do you stop and thank him, giving glory to God and not yourself? These are very tough questions that all boil down to this one: Do you worship God, no matter what?
When you live your life with Christ at the center, people will notice. Living for Christ sets you apart from the world, you cannot help be be different.
If someone asks why you act, react and live the way you do, be prepared to tell them who makes you life possible - give God the glory. This is witnessing. By living set apart in Christ you can share your hope with others.
Simply by sharing a personal relationship with God and living in His ways, people will notice, allowing you to share the promise of salvation Christ grants us all and the joy and peace that follow with others seeking the love only Christ can offer.