Things You'll Need
Instructions
Pour some rubbing alcohol into a small bowl. You just need a little bit.
Dip the end of your cotton swab in the rubbing alcohol. You just need it to be damp, it doesn't need to soak for a long time.
Rub the cotton swab lightly along the contact chip inside the end of the NES cartridge to remove any dust, dirt or other material.
Blow on the inside of the cartridge lightly to dry it, and when it is dry, insert the cartridge into your NES and resume playing.