First trick is to use all of the double and triple score opportunities, even if you have to use a short word. Second - and probably most important - don't take an easy score that sets up your opponent for an even better score. Third, save "s" to make their words plural (or pluralize your own play later) and hand onto "u"'s to go with "q." Other than that, read a thesaurus or practice making words from random letters (anagramming) to start seeing more options.