One of the things that I encouraged my students to do at the recent BetterPhoto Summit photography conference in New York was to approach strangers about making their photograph. It's my belief that at a public cultural event like the New York City Marathon, people are more willing to be photographed than they might be if you just walked up to them on the street. There is a festive and open energy in the air which makes such street photography so much easier, especially for those inexperienced with doing this.
I know that there is a lot of fear and anxiety about approaching people, but it's been my experience that the worst thing is not that they say "no". The worst thing is actually the anxiety and tension we feel at the thought of approaching someone, not the actual rejection when it does happen. And since people say yes more often than they say no, it's a worthwhile thing to do.
There is no easy way to get past the fear. You just have to make the choice to do it, but the more you do, the easier it becomes. It still comes up for me. The anxiety never completely goes away, but for the images I get and the even the occasional "no" is far, far better than the regret I feel for not taking the risk.
The students who took on the challenge produced some wonderful images of people. These are images they might have likely never had made had they not be pushed to do so. The workshops are great as they can help push you to take on such challenges. When it comes down to it, as a photographer you really need to rely on yourself to push you into unfamiliar territory. Otherwise, you're condemning yourself to only make the same images over and over again.
What's the fun in that.
Note: BetterPhoto.com's school of photography offer many excellent online photography classes, including these two by Ibarionex Perello: Portrait Photography Using Available Light and The Pursuit of Light. In addition, Susan and Neil Silverman teach the online digital camera class: Street Photography.