Simply ask the question and listen for the first response that your body/mind gives you. End of story.
For example, today I was wondering what the most important thing for me to do today was in order to best use my time.
Straight away the answer came to me - make a list of what you need to do.
Ok - so not a groundbreaking answer - but nonetheless - correct.
Later, I was checking out a room in a community centre as I am to begin giving meditation lessons soon. I hate driving all over town and am used my lucky knack for (usually) magically stumbling across what I need straight away. But today - as soon as I walked in, I got the gut feeling that this wasn't the place, even though I had spent a good couple of hours in the heat, traffic and negotiating my way through the red tape at the local town hall to get the key (that alone took 45 minutes!). I wasn't quite sure why it wasn't the place - but I just knew I needed to look elsewhere.
No doubt the perfect location awaits me around the corner.
But for tonight - Wing Chun training!