Evangelism

I'm no deep theologian or a sign-toting street evangelist (far from it---I'm still struggling to witness!), but I do know sincerity and a sense of humility will get you a long way with people.
People are people---all of us are sinners, and when we speak about Christ, we're doing it in gentleness and love, not in the heat of a fiery debate or winning the 'faith' argument. Listen and ask questions more than spouting religious dogma, and most of all, act like a concerned friend instead of turning people off with your irritation to 'get the upper hand' of the conversation.
Sure, people may say some stuff that isn't it line with you, but that's why you're convicting them of their sins and handing them the Gospel's truth. It isn't about argument---it's about salvation.
I found Ray Comfort and Kirk Cameron's ways of presenting the gospel really great for future use. (www.livingwaters.com has their videos and presentation.) I've given out their gospel tracts and their fun, unoffensive ways that get people's attention.
Of course, sometimes you can't get a person to change their mind at the moment. That's okay, too. You may have planted a seed that another person will water, and a third will help grow.
(www.NeedGod.com is also a great website, part of livingwaters.)