Take it out, disconnect anything thats attached to it at either end. You can leave the bracket on. Give it a good banging first, lots of loose stuff will fall out. Then, you can unscrew the bottom screws, and you should be able to slide out the filter element. Then, I used a soft bristled brush inside to clean out bits of grass and flies etc.
Then, spray loads of cleaning solution inside (the filtering element itself), and let it soak for 5-10 mins. Then use a tap or hose on low from the clean side to the dirty side to wash away all the dust thats stuck in it. After this, shake off excess water, and let it dry in the sun and wind. When dry, oil it, but not enough to cause any to gather or run off the filter, this is too much. Just enough so that a vigorous shaking will only make a few spots appear on the floor. Then, connect it all back up, minus the MAF, and let it idle for 10 mins. Then turn off the car, reconnect the MAF, make sure the filter is in the best place for getting cold air on the move, and fire her up and take her for a good spin. Enjoy the sound
EDIT:: The idling without MAF bit is important, as it draws off excess oil. If you get this oil on your MAF, you will be coughing up for a new one, and they aren't cheap. A ton is considered about right price for a JTD MAF.