Shut down the computer and disconnect the keyboard. Gently remove each of the keys, making note of where each key goes, or clean them one at a time. The Spacebar has two hooks on the underside. Remember how it comes on and off so it may be easily replaced. Turn the keyboard upside down and tap the bottom of the case to loosen dirt and debris in the keyboard. Turn the keyboard upright and use compressed air to blow out the rest of the debris. Soak a cotton swab with alcohol, and use it to clean the keys and plungers. Let the keyboard fully dry before replacing the keys. If the key is still sticky, the contacts may need cleaning. You can obtain electrical contact cleaner at most electronics and computer stores. Remove the key(s) again. If you can see metal contacts in the hole that the keycap fits it, squirt a little bit of contact cleaner into it. Let the contact cleaner dry for about five minutes, then replace the keycap(s). To clean the tops of the key caps, simply soak a cotton swab with alcohol and slowly rub the soiled areas until the dirt disappears.