1. Ensure to enable HTTPOnly Attribute to make sure that the cookies are protected from attacks such as XSS.
2. Apply the Release Updates to ensure that the system is up to date.
3. Enable Field History Tracking for Custom & Standard Objects to ensure that any unauthorized changes do not go untracked.
4. Implement a salesforce Role Hierarchy to determine how the access controls should be distributed among various user roles and levels.
5. Ensure that the transaction security is in use.
6. Ensure that multi-factor authentication is enabled for all the user accounts.