Here is a link to the MSDN for Clustered Index Design Specifications which may help you better understand what columns you should use for your clustered index.
http://msdn.microsoft.com/en-us/library/ms190639%28v=sql.105%29.aspx
Also, you may want to consider taking a look at the "Stairway to SQL Server Indexes" which explains both clustered and nonclustered indexes