5. Disassemble and clean the computer.
You can find plenty of information online for how to disassemble your Mac. MacRecycling.com offers videos showing how to disassemble plastic 13-inch MacBooks, and iBook G4s. iFixIt has PDF guides for how to take apart almost any MacBook, MacBook Pro, iBook or PowerBook. Make sure you're electrically grounded, too, before working on your computer. Lightly touch the screw on the outside of a wall switch to ground yourself, or use a grounding strap (if you have one).
You'll most likely want to remove the top case, the part of the computer that includes the keyboard and trackpad. In many some cases, you'll have to start at the bottom of the computer and remove many, many screws, ribbons and parts. Using a notebook and an empty ice cube tray to keep track of the many different sizes of screws is a good way to make your life easier when it comes time to putting the computer back together.
With your computer apart, try and find where the liquid has seeped to, and sop it up as best you can. Any liquid you spill is going to have the ability to conduct electricity due to metals, sugars, and salts within. Colas, especially, are very acidic, and can corrode sensitive electronic parts. Even if you drink nothing but food-grade de-ionized water, material on the surface of your computer can be carried by the liquid inside your computer, meaning possible conductivity. Of course, unwanted conductivity is bad for your computer.
If what you spilled was oily or sticky, you can use dilute isopropyl alcohol (IPA, or rubbing alcohol) to try and clean areas with the oil on it. Dip a lint-free cloth in a small amount of alcohol and use the tip of your finger to gently clean areas inside the computer.
6. Let everything dry.
You can use a desk lamp and incandescent bulb to gently warm and dry the disassembled computer. Remember, make sure to clean up anything that will become sticky before you dry the computer. You'll want to make sure everything is completely dry before trying to turn on your computer. No matter how great the compulsion, you should wait at least a day before trying to boot your laptop again.
7. Reassemble the computer and try to boot it.
Have you considered prayer? Prayer sometimes works, too.
8. Test it out.
The keyboard and trackpad will probably be most affected by a spill. Try all the keys and all the functions of the trackpad (like scrolling and tapping). If something isn't working right, there are two possibilities: Either it's not completely dry, or its permanently damaged. Give it another day to dry out, and if it isn't working, chances are it needs to be replaced.
If nothing works, you can still take the hard disk out of the computer, put it in an enclosure and connect it to another Mac. That way, you'll have access to your critical files if you need them.
9. Get Service.
Remember the bad news I mentioned in step 1? Well, here it is: Many warranties (including AppleCare) don't cover liquid damage. In fact, newer Apple laptops include moisture sensors to tell repair technicians if something has leaked inside the case. These sensors -- small dots adhered in specific places inside the laptop case -- are white when dry, but turn red when exposed to liquids. If liquid damage isn't covered, then you have to pay the cost to repair any damaged components. Sorry.
10. Share your story.
With that hard lesson under your belt, I'm sure you'll make sure to keep drinks away from your computer from now. Even so, there are times when even the most careful among us fall prey to liquid damage: The laptop pictured at the top of the article had an unfortunate encounter with a (what was thought to be tightly capped) bottle of cranberry juice inside a backpack.
Do you have a liquid damage horror story? Vent your spleen and leave a comment.
[with help from WikiHow.]
How to save a wet laptop (via Switched)