Configuring People Picker

We have a Sharepoint 2010 environment and it is the people picker is returning some accounts we would like to filter out, or should i say we only want certain results to be returned. IE, domain users, not our service accounts.

To my knowledge the people picker has never been configured. my question is,  is there a way to see what is currently being returned before I make changes. This will help me in determining what I need to filter out.

Any guidance would be appreciated.

Kim