Klauss - I am not aware of any 'requirements' but it would probably be a good idea to talk to someone who knows about them - they are incredibly simple - you basically do exactly as the controller tells you and stay silent during the approach (he will be on continuous transmit anyway and won't hear you). What could be easier? All you need to know is the rate of descent you need for the glidepath you are flying - and set it when told.