One thing I found helpful was to find a "native" transaction that does something similar to what I want then debug it. It was nice to be able to read and debug

One thing I found helpful was to find a "native" transaction that does something similar to what I want then debug it. It was nice to be able to read and debug the existing "SAP" code. Also, that was the only way I remember to find the "user exits" where you can extend an existing transactions.