First off, there are several types of written English. The kind we use here is informal, which means you will see a lot of things from me that you wouldn't see in formal English--such as my predilection for dashes, parentheses, and italics.
Originally Posted by Ronald Brak
It also applies to starting sentences with conjunctions. I wouldn't do it in, oh, college application essays, gods know, but it is a stylistic choice. Starting every sentence (see, there I go) with a conjunction is a bad thing, but a few here and there is no big deal. Heck, I do it all the time. Strunk & White says it's okay to do now and again.
"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"
"You can't erase icing."
"I can't believe it doesn't work! I found it on the internet, man!"