Read as much as possible. Language and words are the primary tools every good lyricist needs. Good lyricists are usually very well read and their reading background provides them with a rich arsenal of ideas, phrases, and images to draw from for their own work.
Study and imitate your favorite lyricists. All artists start off by emulating their heroes. Emulating your heroes involves analyzing and understanding how they hone their craft and develop their skills. For example, numerous contemporary lyricists and songwriters list Bob Dylan as an essential influence on their work. Bob Dylan, in turn, began his songwriting career under the heavy influence of Woody Guthrie.
Carry a notepad with you all the time. Jot down ideas, phrases and experiences that you encounter during the ordinary course of your day.
Find a writing style that works for you. Some lyricists write the lyrics first and then set them to music. Other lyricists write the music first and then write lyrics that fit the music. For example. Bernie Taupin was Elton John's lyricist. Taupin wrote the lyrics first and then Elton John set them to music. Musicians who write the music and the lyrics for their songs often write the music first. The melodic nature or chord structure influences the thematic content for the lyrics.
Write a first draft for a song. Allow the song to sit for a day or two to gain distance from it and then go back and critique and edit it. Replace cliche words and rhymes with less obvious word choices.