1.: Finding related popular keywords, search phrases

1.1.: Start with what you know
1.2.: Prioritize keywords by intent
1.2.1.: Adjusting relevance on the go

Keyword popularity tools, top searches in Google and major search engines:

1.3.: Prioritize by popularity / competition
1.3.1.: Google AdWords (External) Keyword selection tool
1.3.2.: Google Trends
1.3.3.: Google Hot Trends
1.3.4.: Yahoo! Search Marketing ( Self Serve )
1.3.5.: Overture Keyword Selection Tool
1.3.6.: WordTracker
1.3.7.: Keyword Discovery
1.4.: Scale by generalization

2.: Generic tips on popularity, filtering, competition, natural language
2.1.: Popularity vs. projected market share

3.: Summary - (over)using popular phrases
3.1.: The Basics
3.2.: Advanced
3.3.: Expert