I know somebody who has aids and/or hiv, what do I need to do to make sure that me and my family do not come in contact with the disease?

Stay away from street (dirty)needles and watch who you sleep with/who they have been with

http://www.sfaf.org/aids101/transmission.html#transmitted

You don't have unprotected sex with them, and don't have exchange of body fluid

Basically you would do just what everyone should do with anyone that comes to their home.