I am new to SFDC integration code.  I wrote a basic webservice class in APEX and exported the WSDL.  I understand that I'll need a login call to obtain a session id.

Is there a way to add login tags to the class WSDL so that I can use just one WSDL file in the external system?

If so what tags can I add to the class WSDL header or body?

Thanks in advance.