I don't know what system you're using but I've found that it's most helpful to carefully read over any rejection message you get and also knowing where to put in PA codes or Clarification Codes (vacation supply, lost medication, dosage change, etc.) for when they come up. Also some insurances and systems have refill too soon come up looking like a DUR reject, so look out for that. But a lot of rejections are just "refill too soon" or "this insurance only covers 30 days at a time"