How many time do you have found your inkjet printer dead after a standing idle long period? Because of the low durability of inkjet prints I usually send them to a web print-shop, so my colours, althought I try to remember to keep them making exercise, often get dry. This happens more certainly if you go on printing after the warning of ended ink (whoops...).
Anyway... it's not a big problem if you know hot to solve the matter.

Step 1: Remove the Cartridges

Some cheap printers have the head attached to the ink-cartridge, but those cartridges are much more expensive and the quality is worse. My Canon IP4600 is a not very expensive printer, but with a good quality and CD printing too, I love it. It has 5 cartridge which you can extract without moving the head, I've already removed them in the picture.

Step 2: Remove the Head

To remove the printer head you have to pull up the gray lever. The head will come out with no resistance. Pay attention to not touch the rear contacts and the bottom side where you find the ink nozzles. These last are very delicate, don't scratch them with rags or other, also if you see they're covered of ink, anyway it might not dip..

Step 3: Find a Proper Suction Tube

Now you need some luck, but also a good equipped maker shop will be useful. I've searched among the rubber tubes I had, to find one which has the right diameter for the cartridge joints on the printer head. These tubes are not essentials, because probably it's enough dip the head (the printer one, not your!) in water. But I think they'll guarantee the success.

Step 4: Dip Into Water

Set up a plastic flat cover with some millimeters of water. it is important you don't use ceramic plate, or anything else made from an hard material. This because the nozzles borders are ceramic and they break very easily. I know it because I've broke my old IP4200 printer head tapping it on the plate, don't ask me why... I asked myself it a lot of time! probably I didn't want to accept the more obvious reason
;-)
Put the stuff to soak for a while... The water will dissolve the dry ink. Meanwhile with the rubber tube try to suction some water from the plate into the nozzles. To do that you don't necessarily suck the tube, it's better you keep it in place, push the sides, close the open end, and let it sucks for you resuming the original shape. Now you can wait an hour, but if you have time you can leave it all the night.
At the rear side of the printer head, the contacts should be waterproof, but don't wet them too much.

Step 5: Dry the Head

When you have time to reinstall the head on the printer, dry it gently pushing it on a paper napkin, don't rub it, and let the water coming out for a few minutes. It's better use microfibre cloths, so they won't clog up the nozzles with fibers. You should see some coloured lines as in the picture, one for each nozzles line.

Step 6: Almost Done

The printer head is now clean, it still has some water inside, but don't worry about it.

Step 7: As Brand New!

Install back the head into place, close the lever, put the 5 cartridges on, close the printer and turn it off.
I've waited a few minutes now, because I think the ink need time to mixing up with the water inside the head nozzles.
When you turn on the printer again, probably it will want to make the nozzles cleaning, and its right ;-) if not tell it to do that. After the cleaning, which will waste a few quantity of ink, you'll can print the check sheet to verify that all the nozzles are clean and working!