The only advice i can give you regarding NDB approaches = Make sure you have minimum 2 operating ADFs installed, tuned and identified, do not conduct an NDB approach with 1 ADF,GPS backup does occur but unless you have a thorough knowledge about the DO's and DON'Ts with GPS - DON'T'
Why the need for two ADF's?
With modern screens it is very easy to use the GPS bearing pointer to back up the ADF. What are the DO and DON'Ts you refer to?