Hello.There is no guaranteed way.But you can minimize the risks of hacking (but not eliminate it completely).

1. Choose a popular and not the cheapest hosting.
2. Place one site on one hosting account.
3. Use the current version of PHP on the hosting.
4. Regularly make backup copies of site projects and store them in a safe place.
5. Ask your hosting provider, what means of protection and verification they offer.
6. Restrict access to the FTP site by IP address.
7. Use encrypted connection with FTP, for example, SFTP.
8. Use strong passwords for FTP, hosting and databases.
9. Do not trust access to your hosting and computer with the program to unauthorized persons.
10. Install a good antivirus on your computer with WebSite X5 installed.
11. You can restrict access to the administrative panel of the site using ".htaccess".
    
12. You can use SSL.
13. Do not use open free wifi network to connect hosting.
14. Register site in Google Search Console.

There are many more ways to increase security and monitor the site. For example, you can connect third-party services to monitor the site. But in my opinion it will be superfluous.