This is probably the most important aspect of keeping those hackers away. Make sure you have a strong, complicated password (numbers and letters preferably). However, no matter how difficult a password is, it's pointless if you simply give it out. If you need to give it out, do so at your own risk; only people you truly trust, and preferably no one you only know through the game.
Changing your password frequently is a great way to keep your account as safe as possible. Once every few weeks should do the trick. Just be careful to remember your new passwords and try and avoid writing them down. Don't make it easy for people around you to pretend to be you online. It's simple, but if only you know your password, then it is not possible for anyone to gain access to your account.
And what ever you do, don't make your password 'password'...