The key areas are;
The person in these areas should be segregated based on the ARC principle (Authorization, Recording and Custodian), meaning, the person who is initiating a transactions should not have approval rights. Likewise, under receivables the collectors should not have rights to update receivables records, their duty is to submit the money in the form of cash, bank cheques etc. to credit department, in a nutshell, those who record should not have rights to authorization or custodian etc.
The following information should be gathered;
Hope it will help you to some extent.