Can someone see any potential problems with this design, it is my very first attempt and I hope I understand the 3rd Normal form. Any feed back will be greatly appreciated.

Client Table
Client_ID {Primary Key}
Client_Name
Client_Location {Foriegn Key?}

Client Location Table
Client_Location {Primary Key}
State_ID {Foriegn Key?}
District Name

District Code Table
Client_Location {Primary Key [Composite?]}
District_Code_ID {What kinda key is this? Primary 2?}
District_Code

Building Code Table
District_Code_ID {Primary Key [Composite?]}
Building_Code_ID {What kinda key is this? Primary 2?}
Building_Code

Client Contact Table
Client_ID {Composite Key?}
Client_Address_ID {Primary Key?}
Contact_Name
Contact_Email
Contact_Phone
Contact_Fax

Client Address Table
Client_Address_ID {Primary Key}
Client_Address
State_ID {Composit Key?}
City
Zip

Mileage Table
Client_Address_ID {Primary Key?}
Round_Trip_Mileage

Remote Access Table
Client_ID {Primary Key?}
Client_IP
Client_gif_location


Hmmmm, as you can see I am still a lot confused on what kinda Keys there are... all I know is that I think all the tables relate to each other... Can some lend some advice or corrections. I tried to break down the tables to "Single Themed" based... or 3rd Normal Form.

Thanks to everyone who can lend a hand.