Writing the beginning of a story makes me more anxious than any other part. For one thing, it’s my only chance to grab the reader’s attention. Many slush readers decide on the first page whether they’ll pass on a story. Some say the first paragraph or even the first line. No pressure!
Short story and flash fiction writing have been great practice for me in learning to discover the true “inciting incident” that sets everything rolling. I like to start with a bang or a laugh and try to pique the reader’s curiosity.
I know I’m not alone. The beginning is a huge sticking point for many writers. I’d advise others to just write whatever to start with, and then keep in mind that later, it will probably be changed or may even fall to the cutting room floor. I find it helps take pressure off so I can get a story out. Then I’ll only have the smaller problem of fixing the opening at the end, rather than having a blank page while dithering over the perfect beginning.
E. Chris Garrison 
Trying to find the actual beginning of a story is sometimes the hardest part of writing. I have one story (my current WIP, actually) that involves a civillian being dragged behind enemy lines. So far my starting points have included
* When the kidnappee first meets the rest of the characters
* Right when she’s captured
* When she returns home, thoroughly traumatized
* When she’s in the antagonist’s dungeon
* and plenty of variations thereupon
I’ve found what works best for me is to have someone who’s incredibly patient and kind go through and read the first few chapters, and ask them where the story really begins. More often than not, they’ve got a clearer view of the meat of the story than we do.
I agree, it’s essential to have other eyes on my stories to help with things like that and help me see things I can’t.
I would hate to lose whole chapters of a novel though, so if the story really begins in Chapter 3, I will want to somehow salvage as much of the first two chapters as I can… transplant the scenes or work in the background material in some other way.