To secure your Microsoft 365 environment, implement several best practices. Start by enabling multi-factor authentication (MFA) for an added layer of protection. Regularly review and manage user access permissions to ensure only authorized personnel have access to sensitive data. Utilize advanced security features like Microsoft Defender for Office 365 to guard against phishing and malware. Apply data loss prevention (DLP) policies and encryption to protect confidential information. Establish conditional access policies to control access based on user location and device compliance. Finally, keep systems updated with the latest security patches and conduct regular security assessments to identify and address vulnerabilities.