- Visit your business page on Facebook
- In the top right corner, click "Manage" then click "Edit Page" in the dropdown menu
- In the left top area, click "Your Settings"
- Make sure there is no check in the box next to "Always comment and post on your page as (Page Name) even when using Facebook as (Your Name).
- Click "Save Changes"
- Go back to your business page.
- Comment on or "like" existing posts by the page or its fans and it will appear to come from your personal profile.
UPDATE: This setting does not apply to Facebook's mobile application. Your likes, comments and wall posts will always appear to come from your Page, not your Personal Profile.