Data access control is crucial for protecting sensitive information from unauthorized access. It involves defining who can access certain data, ensuring that only authorized users have access. There are four main types of data access control: Discretionary Access Control (DAC), Mandatory Access Control (MAC), Role-Based Access Control (RBAC), and Attribute-Based Access Control (ABAC). Effective strategies for implementing data access control include defining access requirements, selecting an appropriate access control model, setting strong policies, managing access, and auditing. It's essential to use the principle of least privilege, implement strong authentication, monitor and audit access, educate users, and continually review and refine access controls as your business grows.