If you believe in the kindness of strangers, this tip might be for you. Most laptop users fear that their computer will be lost or stolen. Assuming that the right sort of person finds your laptop, however, they might be willing to return it to its rightful owner, if they knew how to contact you.
It is possible to add a short message to the login screen of your Mac. The easiest way to do that is by using Onyx; click on the Parameters tab, and then type your message into the area shown above. I suggest including your name, phone number, and whatever else you think increases your chances of getting it back.
This won't help if a thief has ripped off your MacBook while you weren't looking, but it just might help if you accidentally leave it in a cab and someone trustworthy gets in next. Hey, it could happen!
Note that "certain special characters" includes ( ), so if you want to include a phone number, I suggest using a format such as xxx-xxx-xxxx.