When it comes to songwriting, you should always write what you know. Draw inspiration for your songs from your own life experiences, whether past or present. Take Taylor Swift for example. Swift writes about being a teenager and draws from her own life experiences, resulting in hit after hit. The experiences may be unique but the themes are universal, enabling millions of people to relate to her songs.
While writing songs about your own life experiences is paramount, you should also consider your audience. If you are writing songs for a children's album, for instance, you may want to dial down the teen angst and rely on your own fun childhood experiences for those songs.
Collaborating with others is essential to your growth as a songwriter. It can also lift you out of a writing rut, should you fall into one. Once you find yourself using the same few chords to reinvent songs you've already written, it's time to bring someone else into the mix. Sharing and brainstorming ideas with someone else is fuel for the creative motor. Even if you can't find someone who is a full blown songwriter like yourself, find someone who at least plays a different instrument or a different style of music. You will soon find yourself adding a whole new dimension to your own songwriting style.
Never leave a song unfinished, even if you think it's terrible or cheesy. Remember the adage that we are often our own worst critics. How many times have you heard a song on the radio and thought it was awful? Someone else may love that terrible song of yours too. It's also good discipline as a songwriter to finish every idea. Even if it is still too unfortunate to play, keep the song as a building block for something else before completely discarding it from your repertoire. Go through the lyrics and riffs and pull the best ones to use as an idea for a new song.
While you should finish every song idea, you also shouldn't force one either. If you've got an awesome hook for a song or just a simple verse, but can't think of where to go with it, don't spend all your time trying to force a song that just isn't there yet. Just spend a little time each day or each songwriting session working on the idea and eventually the rest of the song will come to mind. It may just take a little longer for some songs.
Some songwriters write lyrics first, others start with the music. Try both ways until you find the right start for your own creative process. If you start with music, keep jamming out rhythms while humming a melody, without lyrics. Having the melody will help you with syllable and word counts when you sit down to write the lyrics. Alternatively, starting with lyrics and a melody already in your head can sometimes make it easier to sit down and find the right chords and rhythm to go along. Practice different approaches to songwriting until you find a flow that works best for you.
Nashville based songwriter, Tommy R. Smith, among whose hits include "Somebody Paints the Walls" by Tracy Lawrence and "Take the Keys" by Garth Brooks, has some unique advice for new songwriters that he works with. He recommends they "put some 'furniture' in their songs." By 'furniture' he means that they should put something real in each song, like the name of a restaurant, a real name or nicknames of actual people or a brand name of some kind. For example, John Cougar Mellencamp incorporated several pieces of furniture in his hit "Jack and Diane," including the names Jack and Diane, the nickname Jackie, the location Tasty Freeze and the name brand Bobby Brooks.