I'd rather put : "prevent the nightmare from coming true" as a title.. anyway.. let's get to the real thing.. If you want to do
Pick a pro webhoster :
Professional webhosters are experimented in this field. There are people you can trust who know how to protect the server from eventual hack attacks.
Choose good password :
The easiest thing that a hacker would do is to get you password and use it against you.. So you better pick a good one. Good passwords are unguessable, long and contains various caracters type ( letters, numbers, puncts...etc etc), above 15 charachters. This an example of a good password : "g8@"ju$por£%99รง>llop" . Hackers usualy use software to guess your password. So you better make it hard for them as much as you can.
Never use Internet explorer :
Hackers use "Phishing techniks" to "hunt" your password from you browser. If you're using I.E you're increasing the risks of bening hacked. I.E 6.0 was a great disaster to webmasters. I highly recommend Firefox for webmasters because it's safe and contains many web developer tools.
Code properly :
You have to be careful about html and PHP forms that you put into your websites. If you're using PhP/MYSQL hackers could inject codes into your database through you comments form for example.. you can lose all your data. So you'd better learn how to code properly and disable injected scripts into forms.
Make your own backups :
Don't rely on the webhoster to keep a backup for you because it may be hacked too. So you should make your own backups and save them in your hard disk. if you get hacked you'll just change the server or password and use your backup and you website will survive.