Remove the windscreen from your microphone. This is often done by simply screwing the windscreen counterclockwise. Do not use force when attempting to remove the windscreen.
Hand-wash the windscreen with water and a small amount of dish soap. Use a soft toothbrush to remove any residue that does not come off by simply running the windscreen under the faucet.
Allow the windscreen to air dry completely before re-attaching it to the microphone. If you need to re-attach the windscreen immediately, use a hair dryer to thoroughly dry the windscreen. Never attach a damp windscreen onto your microphone.