Hello; The main thing is to keep the new animals or plants separate from others for a sufficient time. For fish some members use quarantine for a few months because some disease takes a long time to show up.
If you do not get an answer on this thread it might be of use to search about amphibian diseases.
Its pretty straight forward, keep in a separate tank, do not use anything would use in your main tank with them or expose your hand to there tank and then main tank with out washing well first.