You use it everyday. You take it for granted. But if you didn't have one, it would be very hard to do what you love to do
It's your keyboard of course.
You know you love it, but do you take good enough care of it? You may regularly clean out your mouse, but have you ever turned your keyboard over and shaken it? If you have a surface that's easily cleanable, you might want to try. Just be prepared for what comes out (especially if you let your cat on the keyboard, those little furry things shed like crazy.)
There are some very technical terms for it, such as keyboard crud, keyboard dandruff, and OMG! What the hell is that?. Yes, this stuff is pretty nasty when accumulated over time. There is prevention, of course, such as keyboard "condoms" and a microphone with some dictation software, but neither of those sound really enticing. What you really need to do is clean it. Here are some of my suggestions:
Before you start, grab some Q-Tips. You should have some lying around somewhere. If you have the fabled geek girlfriend you'll probably find them in the bathroom cupboard. While you’re at it, find a thin metal (nail) file and a wet cloth, a small source of (soapy) water, and a good light source. If you clean your mouse regularly, you may have some small needle-nose pliers, grab those too. And, if you don't want to be "typing" gibberish, unplug your keyboard.
First, turn your keyboard upside down, and shake it for a bit. Try not to breathe in too much. After about 10 seconds of vigorous gyration, put your keyboard aside, and take a look at what fell out. It helps if you have a dark surface. From personal experience, it's mostly dust, hair, crumbs of various kinds, nail clippings, and some of my dead skin. Just take the wet cloth and sweep it away. Repeat these processes as you see fit.
Next, put your keyboard in front of you and scrutinise. It looks harmless, right? Wrong. Look harder. In between the keys... This is where the light source helps. Most of you haven't looked at your keyboard (you rarely need to) so it may be a shock. Attached to the key sides is fine dust that didn't get shaken out. Perhaps some hardened fluid as well. For now, you can leave it be. Look deeper between the keys.
Take the file and, from one end of the keyboard to the other, lightly scrape in between the keys, deep in your keyboard. When you reach the end, try and pry out what you've gathered. Pretty nasty. Hair entangled dust, and maybe some sticky/waxy substance. Throw that out. Do this for the other horizontal gaps in your keyboard. If you need help getting the gunk out at the end of the run, this is where the needle-nose pliers come in handy. Once you've done that, you may notice some stuff still in there, if you wish, you can try to get it, but it's generally not going to come out without rigorous shaking and scraping. Most of you can just leave that and continue.
Before you continue, make sure the file got rid of the crusty stuff on the sides of the keys. Now, take a Q-tip and just run it along the horizontal sides of the keys, much like you did with the file, but lighter. You may need to depress keys, you may not. Just don't force it. It will be covered in dust after one run. Take the other end of the Q-tip and moisten it in the soapy water, not too wet though. Run that along the same area, to get rid of the stuff that needs some wetting. If you need to, focus on a particular key and just get rid of that residue. Do this for all the key lengths. If you need to, go over it again with a clean dry end, to get rid of the wetness.
Once you've got the horizontal parts done, do the vertical. Take a clean dry Q-tip head and "twizzle" it while running it in between two keys. Do this for each pair. Again, if you need to, use a wet head to get rid of some tough grime between keys.
Now that you have the inside and sides of your keys clean (relatively at least) you can work on the top of them. Take the wet cloth, and just wipe over all the keys. If you haven't unplugged your keyboard, avoid hitting Ctrl-Alt-Del. Go wash your hands with soap, and dry them off on a clean towel, and bring the towel with you to your keyboard. Dry off your keys too. With your clean fingers, test the tops of the keys. Some may be greasy, others scratchy. Key's shouldn't be like that. Focus on the nasty keys, and use a Q-tip to degrease, and un-scum the trouble keys. I suggest using the soapy water again on the Q-tip head.
Finally, take the moist cloth (or a clean one if you wish) and go over the non-key part of the board.
Some final notes:
A friend of mine used to have an aerosol can filled with compressed air for cleaning dust. I'm not sure if it came with a little straw or not, but if it didn't, you can grab one from a can of WD-40 (not used of course) and use it. That will help clean the inside of the keyboard after filing, but before Q-tipping.
For those extremists, you can attempt to take off each key, clean the keyboard, and then replace the keys, but I DO NOT endorse this at all.
This process should be done at the very least, monthly, or whenever you're really bored.
Once you've done the keyboard, you can move on to mouse maintenance.