Generate five interesting adjectives and five interesting nouns, then mix and match them to create exciting new metaphors. For example, what can you create out of the adjectives clouded, trembling, underwater, dizzy and clever when you combine them with any of the nouns childhood, dream, maze, helicopter or shadow? Find your own and play with words to get your creativity flowing.
Focus your lyric idea by looking in a thesaurus and/or a dictionary and listing the words associated with your idea.
Try to rhyme words in different ways or use a rhyming dictionary for ideas. For example, if you want to rhyme with the word love, you're not stuck with words like shove, glove, dove and above. You can also use off-rhyme, meaning that only the vowel sounds are the same. In that case, love can rhyme with fuss, up, stuff and even a two-syllable word like because.
List as many cliches as you can think of to remind yourself of what not to do in songwriting. For example, the phrases "til the end of time," "breaking my heart" and "now or never" all fit the definition of a lyrical cliche. You can probably think of dozens more. When writing your song, avoid using any cliche or trite phrase.
Write your song using ideas you got from these creative songwriting exercises. For further inspiration, check out Pat Pattison's book "Writing Better Lyrics" and look online for songwriting communities and websites.