In one of the videos, a commenter mentioned that she was having trouble starting her story because she knows how crucial those first pages are, and didn't know if she could really get it right.
The responses to her dilemma were very good, I thought. The emphasis was on just starting, and worrying about getting it right later. Beginnings are maybe the hardest part, and we talked a while ago here on the bloggy blog about how clear action is what agents and editors look for in a story's opening.
But for our first drafts, the key is to just get words on the page. This YouTube commenter was worried that her first chapter wasn't going to live up to the rest of the story. She was so worried about giving her idea the best start that she couldn't really get it going at all.
The thing is, I know plenty of writers who end up chopping the entire first chapter anyway. On Writing Excuses (the podcast I've mentioned several times and will continue to mention because it's awesome), Brandon Sanderson talks about how he chops the beginnings off his drafts almost every time. For a lot of writers, the beginnings of stories are more to help you as the author set things up, and then become extraneous once the story is done.
Beginnings are important--crucial, in fact--but unlike a racer, you can take as many tries as you need to get things off to a good start. That's what editing is for.
So the point is, don't stress. Just write.