The second lyric writing tool for your list: a thesaurus.
Repeating the same word too often? A good thesaurus will help you find synonyms (words with similar meanings) and may even list some antonyms (words with different meanings) as well.
Despite sounding like an extinct species of dinosaur, a thesaurus will be one your most useful resources. I own Roget’s 21st Century Thesaurus. However, Merriam Webster Online also has a thesaurus feature.
Book
Roget’s 21st Century Thesaurus
Online
Merriam Webster Online