How does one secure a website? Please comment with your answers

Answer 1

Using a Web application firewall (WPF)
Always using SSL for sensitive data
Always sanitise user input.
Always keep up to date with patches
Pick a good host

Answer 2

https://www.owasp.org/index.php/Security_by_Design_Principles

Answer 3

What others said to protect user information and depending on the type of environment I would recommend ddos protection