If you do nothing else then do this. It may seem obvious, but it's amazing how many people still don't do it. There are many ways, but manually on an as-and-when basis is the worst. Automated, preferably wireless systems are best. If you want to really secure your data then data can be sent over the internet to another site.
Secure passwords will prevent most amateurs from accessing your data should your laptop be stolen. Keep a separate list of all your passwords in a safe place. You will need to change passwords on email, bank accounts, facebook, etc. following a theft.
It's relatively easy to encrypt sensitive data held on your laptop, it's built into Apple operating systems. It does have implications, however, so should not be undertaken lightly.
Treat your laptop with respect. Get into the habit of not having food or drink nearby (it's not like spilling into just your keyboard). Don't leave it on show in car or house, and don't leave it on a chair when you've finished with it!
Installing software that allows your Mac to be tracked over the internet if stolen may reduce your insurance costs and increases your chances of getting it back. If it can't be recovered, some software allows remote deletion of data.
With the use of personal laptops for work, and the use of company laptops at home, it may be that you have a legal requirement under the Data Protection Act to take some of the measures outlined above. Even if you just occasionally access work email you may be liable.
What to do if your laptop is damaged? Don't panic.
Call me FIRST! I'll give you free advice on what to do next. You could make things worse.
For friendly advice on how to keep your laptop safe and in working order drop me an email or give me a call 01525 306125