For me, writing the first chapter is the hardest part. That doesn't mean that my first chapters don't turn out well eventually, but if I had a counter on the amounts of times each part of my manuscript faced revision, I would probably find that my first chapter takes the majority of my revision time.
Here is some I've liked or used:
- Start with the most exciting moment.
- Start with something shocking.
- Write the book then delete chapter one (and sometimes two).
Here are some web links about creating first chapters:
Writing the First Chapter
19 Articles about First Chapters
All Kinds of Writing
Children's Books: Writing Great Beginnings