First, be encouraging. It is not unusual for a writer to make an unsuccessful attempt, but to succeed later on.
As an educator, you are in an excellent position to support students developing study plans. Students who do not pass the NGN receive a Candidate’s Performance Report (CPR). This report provides the writer with information about how they did in each section of the exam. Help your students review the CPR and relate it to the content of their nursing program, reminding them of content from earlier years.
The National Council of State Boards of Nursing's (NCSBN's) After the Exam page includes information about using the CPR to help students prepare for re-writing the exam.
Finally, encourage the student to review the prep material on the NCBSN website.