What is the best way to lock views so that reps can only view there accounts
and not others?

Assign a role to a rep that specifies all rights for
accounts are set to the user level (vs. org, parent/child,
or business unit).

Create the role through Home > Settings > Business Unit >
Roles (suggest you copy and modify an existing role).
Then assign the role to a user through Home > Settings >
Business Unit > Users and the Roles side tab.