Start with the forum you're most interested in. If you primarily fly United, the most managable thing to do is lurk over in the United board.
Several FTers have created guides for their favorite airlines. Some resources are...
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MR's Unofficial Guide to United Airlines
(If you're interested in United, please also see my posts
What I've Learned From Flyertalk and
What I've Learned From Flyertalk Part Two.)
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FewMiles' Unofficial Guide to American Airlines AAdvantage
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Delta Flyers' Guide
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ConcordeBoy's Unofficial Onepass Dictionary and Info-site
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More Room Throughout Coach: the Website of Free Miles and Free Markets
[This message has been edited by gleff (edited 12-19-2002).]