I use two words to describe my songs. One word is to describe the music, the other is to describe the lyrical meaning. In my last song the two words I used before I started writing the lyrics were Urgency, the music, searching, the lyrics.
When you do this, the lyrics you write should always have these two words in mind. This way there's always continuity in your message and you don't run aimlessly from one topic to another missing the point. Also because of the vagueness of the two words, it can have several meanings so it still leaves some interpretation for the audience. Searching. Searching for food? Love? Gems in Diablo? You can say what you're looking for but without actually saying it, this way you can relate to larger audiences. Read some Jeremy Enigk.