What are the best practices for securing HTML forms against XSS attacks

Question

I’m working on a web application that involves several user-input forms, and I want to ensure that they are secure against XSS attacks. I’ve read that XSS vulnerabilities can be introduced when user input is not properly sanitized or escaped, but I’m unsure of the specific steps I should take to mitigate these risks.

What are the best practices for securing HTML forms against XSS? Are there any tools or libraries (for example, in Node.js or Python) that can help with input validation and output escaping? I’m looking for practical advice on how to implement these safeguards in a real-world web app.