HR Retention

Hello,
I am the beginner in HR profession. I query is related to HR Retention. My First question is how one can identify the "Tell Tell" sign of retention need in organization. How one can understand that employee is trying to leave the organization or searching for other options outside.
And second question is how we can avoid this situation. What are the retention strategies for that other than money or salary hike. What changes can be done in hr policy.

It depends upon many things, as per my understanding. Work environment and Indivisual career focus places a major role.
If you can help your Employees get promotions or involving them to the core of their responsibilities might help your employee not to think outside your company.
Why should you know whether your EMP are leaving, just make sure you have a good in-house HR team.
Retention strategies would be 3 months notice period where most of your EMP would not make their mind to try outside very often.