Make full and complete inquiries of your client in relation to medical and character issues for all persons in the application (for medical all persons in the family unit). The best way is to ask the client: “If we got a police check today what would it show?” If the client is in any way equivocal then don’t lodge the visa application until you have the police record in (and don’t agree to a fee until you have done so).
Similar with medical – show the client the health criteria (PIC 4005 or 4007) for the visa and ask the client if every member of the family unit passes that criteria.
If there is any complication with either character or medical then ensure that your fee reflects that difficulty.