I was able to get a whole year of printing out of a old deskjet that was thrown out by cleaning it up.
Step 1: Get to Reservoir
You want to first get to reservoir to clean up the caked ink that accumulates there from the ink cartridges. This means that you have to carefully take the printer apart and save all the screws and parts so that you can put it back together again. You may want to document this just in case you get interrupted or you forget what you did last.
Step 2: Messy
When you get to the reservoir it can get messy cleaning up the plastic spindle or wheel that usually has all the ink around it. You might want to wear gloves or do this away from everything. Have something to throw the soiled rag or napkins or whatever your using because it will get very messy and you will want to dispose of the excess ink somewhere.
Step 3: Run a Test
When your done putting it back together you want to reconnect it to your pc and run a color test and alignment test to see how it does.