The key to keeping the right brain switched on is to work quickly without analysing what you're coming up with. Trust your intuition. That thought you had, that thing you said without thinking, that headline you misread, trust it! Don’t discard it because you think it must be wrong or stupid or nonsense - it came from somewhere, it came from your own mind. Resist the urge to “logically” correct your first thought (left brain taking over). There'll be plenty of time for that later, for now we need to get it down and move on.
“Give voice” to that single thought. Don’t question or evaluate, just write it down or record it – even if you have no idea what it means or where it came from. All thoughts come from somewhere so there is a reason for it. Often to work out what it’s about you need to “back off” your thinking (suppress the logical left brain*) and allow the “concept” to blossom. Remember, our right brian is looking at the "whole" bigger picture rather than line 1, verse 1, chorus etc.
The problem we have now is that we want to keep the ideas flowing but we need to “capture” them as well without interrupting the flow. This is where our distraction-free environment becomes important: the phone ringing, the radio going, the cat wanting to go out, are going to interrupt the process.
Another important tool for the serious songwriter is the journal. This may be a notebook, a PDA, the back of an envelope or a minidisc recorder. What is important is that it is always within easy reach and is easy and quick to use. As you improve your right-brain abilities, and as you learn to recognise and value these spontaneous thoughts, you'll need to "journal" them - record them, write them down, whatever. Some people use their cellphone to call their answer-machine! Some have recording mp3 players. Whatever is convenient for your way of working. Don't be caught without it - because if you try to remember it to write down later, your big ol' left brain will have talked you out of it, told you it was dumb or just plain made you forget it.
For right-brain ideas, immediacy is the key. Remember: first thought, best thought.
The following exercise is a method of training your right brain – it is not necessarily a song-writing technique but it may work well for some.
* People who have learned transcendental meditation or other forms of meditation will be familiar with this idea of supression of active thought.