First, keep your password secret. If you need to need to share it with other people, do not forget to change it immediately once they are done with their task. Also, it is necessary to use complex password (combination of numbers, alpha bates special characters) and do not store it in plain text. Changing the passwords periodically is recommended.
 Always use the latest version of third party scripts viz. Blog, forum, shopping cart, themes, templates etc.
 Never keep unwanted data or scripts on your website. If you are installing any script for testing purpose, you should remove it once you test it. Certainly you will forget to upgrade the test script version on your website hence it is advisable to remove such test script from your website.
 The another important point, your personal computer should not be infected by virus, spayware, trojans, keyloggers etc.
 Do not set unnecessary permissions to your files and folders. Generally write permission is not needed to files/folders. Only assign write permission to those files/folders which are necessary.