Attend a poetry class at a local college. The rhymes of famous poets can give inspiration for rhyming ideas. An introductory poetry course is ideal if you haven't taken a poetry class before.
Find a rhyming dictionary. These dictionaries are available for purchase online and at brick-and-mortar bookstores and for free on sites such as the Rhyme Zone website.
Construct rhymes with experimentation. Start with a phrase and pick a word that rhymes with a word from that phrase. For example, "The boat sailed toward the sun. The day was almost done." The words "sun" and "done" form the "true rhyme."