How to Manually Clean an HP Inkjet Cartridge

Unplug the power cord from the printer.
Remove the ink cartridge(s). Check your user manual for specific instructions on how to remove your cartridge from the printer. Once you've removed them, place them wide side down on a paper towel.
Find the copper colored circuitry strip. This is generally located on the back of the cartridge. Clean this portion with a cotton swab containing a little bit of water.
Find the carriage contacts on the ink cartridge. These are located on the back wall of the ink cartridge. Clean these contacts with a cotton swab containing a little bit of water also.
Remove any leftover moisture. Examine both the copper colored circuitry strip and the contacts you've just cleaned. Use a cotton swab to remove any water left on each.
Reinstall your ink cartridge(s). Consult your manual for full directions on how to do that. Be sure all moisture is removed from the ink cartridge before reinstalling.