One technique that’s used by many songwriters is ‘Idea Collection’. Although there are numerous approached the basic premise is always the same.
Here’s how it works. Let’s say you were going to work on a song about jealousy. You’d start by writing down whatever popped into your head about the subject: hate, broken heart, loss, other man, ring, alone, loneliness, anger, trust, insecurity, no answer on the phone, broken promises, unfair, juvenile, lover, etc. Try to list as many ideas as possible. They can be a word, a phrase, a concept, whatever.
It’s important that you’re non-judgmental during this process. Be sure not to be critical of any of your ideas. Just keep jotting them down. Quantity is more important than quality for this to work.
Now start writing your jealousy song. If you’re like most songwriters there will be times when you can’t come up with anything. That would be the time to review your ‘Idea Collection’. You’ll find that often there’s a better word or concept that you can use or perhaps a direction to go in for the bridge.
I think that this approach can be helpful because of the freedom you allow during the creative process of compiling the Collection. When you’re actually writing the song your brain is multi-tasking. It’s thinking about the song form or the rhyming scheme or the meter. If you can free it up a bit with the ‘Idea Collection’ it can work much more effectively.