What's step I, on learning SEARCH?

This depends a lot on what you're precisely trying to learn. Are you wanting to learn to build a search engine, to make your content findable by search engines, to use search effectively?

A good place to start in understanding search, is with the new book Search Patterns. Here's the book's description:

Search is among the most disruptive innovations of our time. It influences what we buy and where we go. It shapes how we learn and what we believe. This provocative and inspiring book explores design patterns that apply across the categories of web, ecommerce, enterprise, desktop, mobile, social, and realtime search and discovery. Using colorful illustrations and examples, the authors bring modern information retrieval to life, covering such diverse topics as relevance ranking, faceted navigation, multi-touch, and augmented reality. Search Patterns challenges us to invent the future of discovery while serving as a practical guide to help us make search better today.

There's also an interview with Peter Morville, the author of Search Patterns, where he describes some of the problems of search and its importance. Search is the Web's fun and wicked problem

If you're more interested in Search Engine Optimization and learning about how to make your content more searchable/findable, you might be interested in The Art of SEO: Mastering Search Engine Optimization and SEO Warrior: Essential Techniques for Increasing Web Visibility.