The Language Construction Kit and Advanced Language Construction explained how to create grammars for constructed languages. But after creating a grammar, there's the 800-pound gorilla of the lexicon to deal with.
This book gives you everything you need to know to create words. The first stop is etymology: it contains thousands of etymologies from a wide variety of languages. Borrow them or let them spark your own ideas!
It's easy to let the lexicon be a coded version of your native language. The Lexipedia contains tips on how to avoid this, including plenty of fascinating examples from non-English languages.
You want to know which words to create first. The Lexipedia includes the 1500 words most commonly found in fantasy and science fiction, sorted by frequency.
Many parts of the lexicon require real-world knowledge to handle. The Lexipedia contains just enough information on biology, physics, and human cultures to help you out.
Plus, there's a discussion of the basic tools of the word creator: categories, metaphors, and derivation.
Though aimed at conlangers, the Lexipedia will be instructive and entertaining for anyone who's interested in words.
Mark Rosenfelder also known as Zompist, is an American amateur linguist and computer programmer, creator of a fictional world called "Almea".