4. Don't Store Passwords
It doesn't matter how many obscure punctuation marks your password has if your computer automatically remembers all of your passwords. Be wary of using password-management programs such as LastPass on anything that could be stolen (it's okay to stick LastPass on your 40-pound desktop, if you wish). You should also refrain from typing all of your passwords into a plain-text file on your computer.
[For tips on building secure, memorable passwords, check out "How to Build Better Passwords Without Losing Your Mind."]
If you lose your laptop, you should still take the precautionary measure of changing all of the passwords to your online accounts, just in case something slipped through the cracks. Also remember to file a police report and consider identity theft protection programs, especially if you ever made an online purchase using the laptop.
5. Get Insurance
You can find multiple kinds of insurance that will cover your laptop being stolen, lost, or dropped.
The first place to check is with the laptop's manufacturer: Many companies offer extra insurance (for an extra fee, naturally). You can also check with the store you purchased the laptop from--retailers like Best Buy typically sell extended warranties. Keep in mind, though, that extended warranties sometimes offer accident protection but rarely provide theft protection, so you may want to skip these plans if your main fear is losing your laptop.
If you can't get your laptop adequately insured by the manufacturer or by the store you purchased it from, take a look at your renter's or homeowner's insurance. Many renter's and homeowner's policies insure all of your private property, no matter where it is when it's stolen. These policies vary greatly, but usually they are limited to theft, vandalism, fire, and flooding--not accidental coffee spills or a fall from a windowsill.
If you use your laptop primarily for business purposes, your business's insurance policy may also cover it.
Beyond those options, if you still can't find the coverage you want, you can always consult third-party laptop and electronics insurance companies. These services offer the most comprehensive coverage for a notebook, though they can be expensive if your machine is already covered under another insurance policy. Safeware offers stand-alone notebook insurance that covers everything from theft and vandalism to cracked screens, accidental damage, and liquid spills.
I have not used Safeware personally, but I have used the similar, student-specific coverage from CSI Insurance Agency. It protects electronic equipment from theft, fire, floods, earthquakes, vandalism, electrical damage, water damage, and accidental damage. While I had CSI, I successfully filed three claims (one for laptop damage, and two for stolen cameras).
Even if you take all of these precautionary steps, having your laptop stolen will still be painful. But it will be less painful if you know that your files are backed up, your passwords are safe, your insurance company will pay for the loss, and you have a very real chance of catching the crook.