I'm not sure if there are any other factors but I'm not sure.
A hacker can steal your domain by accessing your email or accessing into your domain management area. To gain access to your email account or domain area he/she must obtain your password somehow right? Even if you have virus protection on your computer and makes you think you're in safe you're wrong since a hacker can gain access to your computer by finding open ports. So that I highly suggest a professional and good Firewall. Also some security scanners to scan your computer for open ports, backdoors/trojans/keyloggers would be great.
That is the way I do. I have virus and firewall protection. Firewall prompts for every single action happening on my comp. I also regularly scan my computers for the factors I mentioned above (keyloggers,backdoors,trojans etc...)
BTW There are many other methods to gain access to someone's email account. For example : Fake Mails. These are usually emails with the same design of most email providers such as Hotmail, Yahoo etc... When you open such emails, for example, a login page comes up asking your user and password. And it goes on like this...
Some fake mails for outlook kinda appplications contains false links. These emails look like it's being sent from your original dn registrar however most of them has fake links. For example the email is "Your domain on Godaddy is about to expire. Please login to your account by clicking here" (Usually the "by clicking here" link goes to an ip that hacker arranged and the page you arrive normally has the same design of your registrar and there are people, still, being cheated with such methods...
That's all in my mind at the moment.
Stay away from hackers...