In answer to the thread, of course...
What have you got to lose? It's all about taking chances, if all goes well then great, if it doesn't, at least you'll hopefully have some confidence for next time...
Depends on the person, if someone came up to me and started talking to me...i could either be incredibly flattered yet feel bad because i don't fancy the person, or i could be really into her as well and really glad she came over and started talking to me...but you'll never know if you don't try...
Just start off with easy stuff, 'oh do you have the time?' ...do you go to school xyz?' etc.. or maybe try and catch him off guard and make a witty observation about the weather or some other such irrelevant topic...