There are many different questions someone might have about cross country skiing. My advice: rent first, go to a touring center with good grooming, and take at least one lesson. I know from experience how hard it is to self-learn the sport.
But if you do it the bootstrap way, here’s a few links to get you started:
Staight from the ‘snowpros’ (Professional Ski Instructors of America, or PSIA):
Other intro videos
Literally getting started:
Getting Started in Cross Country Skiing
An expert instructor showing how to stop:
How to stop on Cross Country Skis
Yes, they’re all Canadian. One was at Canmore Nordic Centre Provincial Park, and the other at Silver Star-Sovereign Lakes.
The “Here’s what I learned” approach
This blog posting gives some pointers, including a bit on the inevitability of falling, in a comforting and casual tone: Embrace the Wobble and Six Other Lessons I Learned As a Novice Cross-country Skier
Across the Snow Line 