[dba-SQLServer] Testing UDFs

I am jumping into writing UDFs this morning.  I need to test the results.  When I write a query to 
pull data from a table using the UDF as one of the columns (just to display what happens) I get:

"uf_AddrValid not a recognized built-in function name."

Is there a naming convention to allow SQL Server (2005) to understand my UDF and use them?  I know 
that there was a prefix I had to use in stored procedures.

-- 
John W. Colby
www.ColbyConsulting.com