First thing you need to do is remove the filter by unfastening the clamp that holds it to the mass airflow sensor.  Once this is done you need to push off any leaves or other debris that may have become attached to the filter.  The next step is to generously apply some type of filter cleaner as seen below.  I use K&N filter cleaner due to the fact that it is readily available.  The one downside is that the K&N oil may dye your filter if it is a light color, any color other then red or black.  If you have such a filter I recommend using the slightly more expensive Weapon R cleaning kit.

         Now, let the filter sit about ten minutes so the cleaner can do its work.  After the cleaning solution has worked its way in wash it off from the inside out out as to push dirt back out not in.  

         I let the filter air dry at this point, which took approximately 25 minutes.  Air drying is by far the best way to go.  It is important that you don't use heat or compressed air to speed drying.

         After the filter is thoroughly dry re-oil by spraying from about 5 inches while turning the filter.  Make sure the entire surface area of the filter is covered.  Wipe off any over sprayed oil and let the filter sit for another 20 minutes.  Once the oil has dried you can reattach the filter and re-ziptie it in place.  This process should be repeated every 3,000 to 5,000 miles to keep the performance as high as possible.